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At least 217 records · Page 12Linked to original sources

PubMed2006

Homocysteine, folate, and vitamin B-12 and cognitive performance in older Chinese adults: findings from the Singapore Longitudinal Ageing Study.

BACKGROUND: The relations of elevated homocysteine, low folate, and vitamin B-12 with cognitive performance in nondemented elderly are not well established. Limited research data suggest differential effects of homocysteine and folate on specific cognitive domains. OBJECTIVE: The aim was to examine the independent associations of homocysteine, folate, and vitamin B-12 with cognitive performance in high-functioning elderly Chinese. DESIGN: Homocysteine, folate, and vitamin B-12 concentrations were measured in fasting blood samples of 451 Chinese aged >or=55 y with Mini-Mental State Examination scores >or=24 and who were considered fully independent based on Activities of Daily Living score. Cognitive functions were assessed by a neuropsychological test battery. Independent associations (standardized beta) were determined in multiple linear regression models that simultaneously controlled for potential confounders. RESULTS: Log-transformed homocysteine was inversely associated with performance on Block Design (beta = -0.319, P = 0.006) and the written Symbol Digit Modality Test (beta = -0.129, P = 0.031). Log-transformed folate was significantly associated with Rey Auditory Verbal Learning Test delayed recall (beta = 0.139, P = 0.010), verbal learning (beta = 0.112, P = 0.038), percentage of forgetting (beta = -0.139, P = 0.013), and the Categorical Verbal Fluency test (beta = 0.104, P = 0.042). Vitamin B-12 was not significantly associated with any cognitive test score. CONCLUSIONS: In this high-functioning elderly Chinese population, elevated homocysteine is associated with deficits in constructional ability and processing speed and folate is associated with measures of episodic memory and language. Our results provide support for differential effects of homocysteine and folate on specific cognitive functions.

Aged↗

PubMedDate not supplied

Depletion of liver and esophageal epithelium vitamin A after chronic moderate ethanol consumption in rats: inverse relation to zinc nutriture.

This study was designed to determine whether chronic moderate ethanol ingestion alters the levels of vitamin A of liver and esophageal epithelium and if this is dependent on zinc nutriture. Forty male Sprague-Dawley 4-week-old rats were divided into five groups: zinc-deficient (0.9 ppm), ethanol-fed; zinc-deficient; zinc-adequate (25 ppm); zinc-adequate (25 ppm), ethanol-fed; and zinc-supplemented (50 ppm), ethanol-fed. All rats received liquid Lieber-DeCarli diet containing 4,000 IU per liter of vitamin A for 5 weeks. Zinc-deficient, ethanol-fed rats and zinc-adequate, ethanol-fed rats and zinc-supplemented, ethanol-fed rats received 15.5% of the caloric intake as ethanol while zinc-deficient and zinc-adequate rats received isocaloric amounts of maltose dextrin. All groups were pair-fed to zinc-deficient, ethanol-fed rats. In addition, a group of eight rats designated as weight-restricted controls were fed a diet similar to the one given to zinc-adequate rats but in the amount to obtain a final weight as in the zinc-deficient group. After 35 days, the liver histology was normal in all rats, and no fat accumulation was noted. Hepatic vitamin A concentration was significantly decreased in zinc-adequate, ethanol-fed rats (41 +/- 10 micrograms per gm) and further in zinc-supplemented, ethanol-fed rats (12 +/- 5 micrograms per gm) as compared to controls (137 +/- 49). A highly significant negative correlation between serum zinc and liver vitamin A was found in ethanol-fed animals.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1993

A three-dimensional spin-echo or inversion pulse.

In theory, multidimensional pulses can be designed to be selective in any number of dimensions. In practice, available gradient power has enforced a limit to two dimensions. We show here that three-dimensional pi pulses are feasible on commercial imaging machines provided that the range of off-resonance frequencies are limited.

Image Processing, Computer-Assisted↗

PubMed2003

Head excursion of restrained human volunteers and hybrid III dummies in steady state rollover tests.

Seatbelts provide substantial benefits in rollover crashes, yet occupants still receive head and neck injuries from contacting the vehicle roof interior when the roof exterior strikes the ground. Prior research has evaluated rollover restraint performance utilizing anthropomorphic test devices (dummies), but little dynamic testing has been done with human volunteers to learn how they move during rollovers. In this study, the vertical excursion of the head of restrained dummies and human subjects was measured in a vehicle being rotated about its longitudinal roll axis at roll rates from 180-to-360 deg/sec and under static inversion conditions. The vehicle's restraint design was the commonly used 3-point seatbelt with continuous loop webbing and a sliding latch plate. This paper presents an analysis of the observed occupant motion and provides a comparison of dummy and human motion under similar test conditions. Thirty-five tests (eighteen static and seventeen dynamic) were completed using two different sizes of dummies and human subjects in both near and far-side roll directions. The research indicates that far-side rollovers cause the restrained test subjects to have greater head excursion than near-side rollovers, and that static inversion testing underestimates head excursion for far-side occupants. Human vertical head excursion of up to 200 mm was found at a roll rate of 220 deg/sec. Humans exhibit greater variability in head excursion in comparison to dummies. Transfer of seatbelt webbing through the latch plate did not correlate directly with differences in head excursion.

Accidents, Traffic↗

PubMed1999

Components of variance and intraclass correlations for the design of community-based surveys and intervention studies: data from the Health Survey for England 1994.

The authors estimated components of variance and intraclass correlation coefficients (ICCs) to aid in the design of complex surveys and community intervention studies by analyzing data from the Health Survey for England 1994. This cross-sectional survey of English adults included data on a range of lifestyle risk factors and health outcomes. For the survey, households were sampled in 720 postal code sectors nested within 177 district health authorities and 14 regional health authorities. Study subjects were adults aged 16 years or more. ICCs and components of variance were estimated from a nested random-effects analysis of variance. Results are presented at the district health authority, postal code sector, and household levels. Between-cluster variation was evident at each level of clustering. In these data, ICCs were inversely related to cluster size, but design effects could be substantial when the cluster size was large. Most ICCs were below 0.01 at the district health authority level, and they were mostly below 0.05 at the postal code sector level. At the household level, many ICCs were in the range of 0.0-0.3. These data may provide useful information for the design of epidemiologic studies in which the units sampled or allocated range in size from households to large administrative areas.

Cluster Analysis↗

PubMed2004

Reliability of isokinetic ankle inversion- and eversion-strength measurement in neutral foot position, using the Biodex dynamometer.

This study was designed to investigate the intratester and intertester reliability of isokinetic ankle inversion and eversion-strength measurement in neutral foot position in healthy adults using the Biodex dynamometer. Twenty-five men and women performed five maximal concentric contractions at 60 and 180 degrees/s angular velocities. Two physicians tested each subject. The first physician applied the test four times, and the second physician three times. Reliability of peak torque was assessed by calculating the intraclass correlation coefficient (ICC). At both angular velocities, inversion strength was greater than eversion, and when the angular velocity was increased, inversion and eversion strength were decreased, as tested by both physicians. The first measurements of inversion and eversion strength of the first physician were significantly lower than the other measurements (p<0.01). The intratester ICCs for ankle inversion in healthy young adults were highly reliable (ICC 0.92-0.96), and for the eversion values ranged from 0.87 to 0.94. Intertester ICCs for ankle inversion and eversion peak torque values demonstrated a value of 0.95. Isokinetic tests of ankle inversion and eversion strength at 60 and 180 degrees/s angular velocities in neutral foot position for healthy adults are highly reliable with the Biodex dynamometer.

Adult↗

PubMed1990

Noninvasive recovery of epicardial potentials in a realistic heart-torso geometry. Normal sinus rhythm.

The inverse problem in electrocardiography implies the reconstruction of electrical events within the heart from information measured noninvasively on the body surface. Deduction of these electrical events is possible from measured epicardial potentials, and, thus, a noninvasive method of recovering epicardial potentials from body surface data is useful in experimental and clinical studies. In the present study, an inverse method that uses Tikhonov regularization was shown to reconstruct, with good accuracy, important events in cardiac excitation. The inverse procedure was employed on data obtained from a human-torso tank in which a beating canine heart was placed in the correct anatomical position. Comparison with the actual, measured epicardial potentials indicates that positions and shapes of potential features (maxima, minima, zero potential line, saddles, etc.) are recovered with good accuracy throughout the QRS. An error in position of up to 1 cm is typical, while amplitudes are slightly diminished. In addition, application was extended from the above setting, in which the geometry was precisely known and potentials at a large number of leads were measured accurately, to a situation that is more representative of clinical and experimental settings. Effects of inaccuracy in location of the position of the heart were examined. A stylized torso that approximates the actual geometry was designed, and its performance in the inverse computations was evaluated. A systematic method of reduction of the number of leads on the body surface was proposed, and the resulting lead configurations were evaluated in terms of the accuracy of inverse solutions. The results indicate that the inverse problem can be stabilized with respect to different types of uncertainties in measured data and offer promise in the use of the inverse procedure in clinical and experimental situations.

Animals↗

PubMed1995

Low-grade astrocytoma with a complex four-breakpoint inversion of chromosome 8 as the sole cytogenetic aberration.

We report a case of a low-grade astrocytoma in a 10-year-old boy in which the sole cytogenetic aberration was a complex four-breakpoint inversion of chromosome 8 with the karyotype designation 46,XY,der(8)inv(8)(p23q24)inv(8)(q11q21). Two protooncogenes on chromosome 8, MOS at 8q11 and MYC at 8q24, are located at or near the bands which correspond to two of the breakpoints in this inversion. The localization of the structural aberrations to four breakpoints on chromosome 8 provides a rare example of a solid tumor with structural aberrations limited to a single chromosome.

Astrocytoma↗

PubMed2004

Simultaneous MRI acquisition of blood volume, blood flow, and blood oxygenation information during brain activation.

Simultaneous acquisition of complementary functional hemodynamic indices reflecting different aspects of brain activity would be a valuable tool for functional brain-imaging studies offering enhanced detection power and improved data interpretation. As such, a new MRI technique is presented that is able to achieve concurrent acquisition of three hemodynamic images based primarily on the changes of cerebral blood volume, blood flow, and blood oxygenation, respectively, associated with brain activation. Specifically, an inversion recovery pulse sequence has been designed to measure VASO (vascular space occupancy), ASL (arterial spin labeling) perfusion, and BOLD (blood-oxygenation-level-dependent) signals in a single scan. The MR signal characteristics in this sequence were analyzed, and image parameters were optimized for the simultaneous acquisition of these functional images. The feasibility and efficacy of the new technique were assessed by brain activation experiments with visual stimulation paradigms. Experiments on healthy volunteers showed that this technique provided efficient image acquisition, and thus higher contrast-to-noise ratio per unit time, compared with conventional techniques collecting these functional images separately. In addition, it was demonstrated that the proposed technique was able to be utilized in event-related functional MRI experiments, with potential advantages of obtaining accurate transient information of the activation-induced hemodynamic responses.

Blood Flow Velocity↗

PubMed1996

Modulation of immune response to rDNA hepatitis B vaccination by psychological stress.

In a previous study it was shown that antibody formation after vaccination with a low-dose recombinant DNA (rDNA) hepatitis B vaccine was negatively influenced by psychological stress. The present study was designed to assess whether the same inverse relation between HBs-antibody levels and psychological stress could be observed, while administering the standard, and thus higher, dose of vaccine. Volunteers (n = 68) scoring extremely low or high on a combination of questionnaires measuring daily problems and psychoneurotic symptoms were selected for participation. Antibody levels were determined 2, 6, and 7 months after the first vaccination. Questionnaires were completed before entering the study and at month 6. In contrast to the previous study, psychological stress was not found to be related to the antibody levels at any timepoint. These results suggest that, under certain conditions, stress-induced immunomodulation in vivo might be dependent on antigen dose.

Adolescent↗

PubMed1998

Induction of somatic intrachromosomal recombination inversion events by cyclophosphamide in a transgenic mouse model.

Somatic intrachromosomal recombination (SICR) can result in chromosomal inversion and deletion, mechanisms which are important in carcinogenesis. We have utilised a transgenic mouse model to study SICR inversion events in spleen cells. The transgenic construct is designed so that expression of an Escherichia coli lacZ transgene only occurs in a cell when an SICR inversion event occurs in the region of the transgene. The inversion events can then be detected by histochemical staining of frozen spleen sections for transgene expression and by polymerase chain reaction across the inversion breakpoints. The spontaneous inversion frequency in spleen rose 2-fold from 1.54 +/- 0.24 x 10(-4) (mean +/- SE) in 4-month-old transgenic mice to 3.12 +/- 0.67 x 10(-4) in 22-month-old mice. Four- or 8-month-old mice were treated with a single intraperitoneal injection of cyclophosphamide, with doses ranging from 0.01 to 100 mg/kg. The animals were killed 3 days after treatment. A significant induction of SICR inversions was detected at all doses with a 3.2-fold maximum induction of inversions detected at 10 mg/kg. These results suggest that the transgenic mouse model used here may be a sensitive model for studying the role of SICR in mutation and in studying risk assessment of environmental DNA-damaging agents.

Animals↗

PubMed2002

Molecular analysis of an endopolygalacturonase gene from a Eucalyptus canker pathogen, Cryphonectria cubensis.

Cryphonectria cubensis causes a serious Eucalyptus canker disease. Fungal cell wall degrading enzymes (CWDEs) are important during the early stages of interaction of the fungus with Eucalyptus. To improve our understanding of the molecular regulation of the interaction of Eucalyptus and C. cubensis, the relevant genes involved in this interaction should be identified, cloned and studied. The aim of this study was, therefore, to clone the endopolygalacturonase (endoPG) gene of C. cubensis. C. cubensis was grown on a medium supplemented with Eucalyptus cell wall extracts. Degenerate primers were designed to amplify part of the endoPG gene from C. cubensis genomic DNA. The resulting sequence was used to design specific primers for use in inverse PCR to amplify the entire endoPG gene of C. cubensis (ccen-1). The endoPG sequence of C. cubensis has 93% amino acid sequence similarity to that of the chestnut blight pathogen, Cryphonectria parasitica.

Amino Acid Sequence↗

PubMed2001

alpha-Linolenic acid intake is not beneficially associated with 10-y risk of coronary artery disease incidence: the Zutphen Elderly Study.

BACKGROUND: Data on the relation between alpha-linolenic acid intake and coronary artery disease (CAD) are limited. Other dietary components appear to modify the reported relation between alpha-linolenic acid intake and CAD. OBJECTIVE: We examined whether dietary alpha-linolenic acid intake was inversely associated with risk of CAD. DESIGN: We prospectively studied 667 men aged 64-84 y from the Zutphen Elderly Study who were free of CAD at baseline. Dietary intake was assessed by using a cross-check dietary history method. RESULTS: During the 10-y follow-up, we documented 98 cases of CAD. After adjustment for age, standard coronary risk factors, and intake of trans fatty acids and other nutrients, alpha-linolenic acid intake was not significantly associated with CAD risk. The relative risk of CAD for the highest compared with the lowest tertile of alpha-linolenic acid intake was 1.68 (95% CI: 0.86, 3.29). alpha-Linolenic acid intake from sources containing trans fatty acids was also nonsignificantly, yet positively, associated with CAD risk. alpha-Linolenic acid intake from foods that did not contain trans fatty acids was not associated with CAD risk, the relative risk of CAD for the highest compared with the lowest tertile was 1.15 (95% CI: 0.63, 2.11). CONCLUSION: We did not observe a beneficial effect of dietary alpha-linolenic acid intake on the risk of 10-y CAD incidence. Investigating this hypothesis was complicated by the association between intakes of alpha-linolenic acid and trans fatty acids. Given the results of current prospective studies, a protective cardiac effect of alpha-linolenic acid is questionable.

Aged↗

PubMed2001

Somatic mutation in human T-cell leukemia virus type 1 provirus and flanking cellular sequences during clonal expansion in vivo.

BACKGROUND: Human T-cell leukemia virus type 1 (HTLV-1), the causative agent of adult T-cell leukemia/lymphoma, shows intrapatient genetic variability. Although HTLV-1 can replicate via the reverse transcription of virion RNA to a double-stranded DNA provirus (the conventional manner for retroviruses), its predominant mode of replication is via the clonal expansion (mitosis) of the infected cell. This expansion is achieved by the viral oncoprotein Tax, which keeps the infected CD4 T lymphocyte cycling. Because Tax also interferes with cellular DNA repair pathways, we investigated whether somatic mutations of the provirus that occur during the division of infected cells could account for HTLV-1 genetic variability. METHODS: An inverse polymerase chain reaction strategy was designed to distinguish somatic mutations from reverse transcription-associated substitutions. This strategy allows the proviral sequences to be isolated together with flanking cellular sequences. Using this method, we sequenced 208 HTLV-1 provirus 3' segments, together with their integration sites, belonging to 29 distinct circulating cellular clones from infected individuals. RESULTS: For 60% of the clones, 8%-80% of infected cells harbored a mutated HTLV-1 provirus, without evidence of reverse transcription-associated mutations. Mutations within flanking cellular sequences were also identified at a frequency of 2.8 x 10(-4) substitution per base pair. Some of these clones carried multiple discrete substitutions or deletions, indicating progressive accumulation of mutations during clonal expansion. The overall frequency of somatic mutations increased with the degree of proliferation of infected T cells. CONCLUSIONS: These data indicate that, in vivo, HTLV-1 variation results mainly from postintegration events that consist of somatic mutations of the proviral sequence occurring during clonal expansion. The finding of substitutions in flanking sequences suggests that somatic mutations occurring after integration, presumably coupled with selection, help move the cellular clones toward a transformed phenotype, of which adult T-cell leukemia/lymphoma is the end point.

Adult↗

PubMed1998

Beyond 'knock-out' mice: new perspectives for the programmed modification of the mammalian genome.

The emergence of gene inactivation by homologous recombination methodology in embryonic stem cells has revolutionized the field of mouse genetics. Indeed, the availability of a rapidly growing number of mouse null mutants has represented an invaluable source of knowledge on mammalian development, cellular biology and physiology and has provided many models for human inherited diseases. In recent years, improvements of the original 'knock-out' strategy, as well as the exploitation of exogenous enzymatic systems that are active in the recombination process, have considerably extended the range of genetic manipulations that can be produced. For example, it is now possible to create a mouse bearing a targeted point mutation as the unique change in its entire genome therefore allowing very fine dissection of gene function in vivo. Chromosome alterations such as large deletions, inversions or translocations can also be designed and will facilitate the global functional analysis of the mouse genome. This will extend the possibilities of creating models of human pathologies that frequently originate from various chromosomal disorders. Finally, the advent of methods allowing conditional gene targeting will open the way for the analysis of the consequence of a particular mutation in a defined organ and at a specific time during the life of a mouse.

Animals↗

PubMed2005

Design and analysis of a general recurrent neural network model for time-varying matrix inversion.

Following the idea of using first-order time derivatives, this paper presents a general recurrent neural network (RNN) model for online inversion of time-varying matrices. Different kinds of activation functions are investigated to guarantee the global exponential convergence of the neural model to the exact inverse of a given time-varying matrix. The robustness of the proposed neural model is also studied with respect to different activation functions and various implementation errors. Simulation results, including the application to kinematic control of redundant manipulators, substantiate the theoretical analysis and demonstrate the efficacy of the neural model on time-varying matrix inversion, especially when using a power-sigmoid activation function.

Algorithms↗

PubMed2004

Effects of pulse rate and electrode array design on intensity discrimination in cochlear implant users.

The effects of pulse rate on intensity discrimination were evaluated in 14 subjects with Clarion C-I cochlear implants. Subjects had a standard [Clarion spiral electrode array (SPRL group)] or perimodiolar electrode array [Clarion HiFocus electrode array with electrode positioning system (HF+EPS group)]. Weber fractions for intensity discrimination [ Wf(dB)= 10 log deltaI/I] were evaluated at five levels over dynamic range at each of three pulse rates (200, 1625 and 6500 pps) using monopolar stimulation. Weber fractions were smaller for 200 pps stimuli than for 1625 or 6500 pps stimuli in both groups. Weber fractions were significantly smaller for SPRL subjects (mean Wf(dB) = -9.1 dB) than for HF+EPS subjects (mean Wf(dB) = -6.7 dB). Intensity difference limens (DLs) expressed as a percentage of dynamic range (DR) (deltaI%DR= deltaI/DRdB* 100) did not vary systematically with pulse rate in either group. Larger intensity DLs combined with smaller dynamic ranges led to fewer intensity steps over the dynamic range for HF+EPS subjects (average 9 steps) compared to SPRL subjects (average 23 steps). The observed effects of pulse rate and electrode array design may stem primarily from an inverse relationship between absolute current amplitude and the size of intensity DLs. The combination of smaller dynamic ranges and larger Weber fractions in HF+EPS subjects could be the result of increased variability of neural outputs in these subjects.

Adult↗

PubMed1997

The effect of sudden inversion stress on EMG activity of the peroneal and tibialis anterior muscles in the chronically unstable ankle.

Residual symptoms resulting from recurrent episodes of inversion-type ankle sprains may be attributed to a decreased neuromuscular response of the peroneal or tibialis anterior muscles, thereby increasing the probability for reinjury. The purpose of this study was to examine the electromyographic (EMG) response time of the peroneal and tibialis anterior muscles in response to sudden plantar flexion/inversion stress in the chronically functional unstable and normal ankle. Subjects for this study consisted of 13 athletically active individuals (five males and eight females, mean age = 19.2 +/- 1.51 years) with a previous history of a unilateral inversion-type ankle sprain. A specially designed platform that allows each foot to drop into plantar flexion/inversion from a standing neutral position was used. Reaction time in milliseconds for the peroneal and tibialis anterior muscles to sudden plantar flexion/inversion was measured via surface EMG. A paired t test was performed with the Bonferroni-Dunn correction factor to determine differences between the peroneal and tibialis anterior as well as between the chronically unstable and contralateral normal ankle. The results indicated no significant differences between the stable and unstable ankles for the peroneal or the tibialis anterior muscles. The results also indicated no significant differences existed between the tibialis anterior and peroneal muscles in either the stable or unstable ankles. The findings from the present study suggest that self-reported functional ankle instability may not result in a diminished reflex response time of the peroneal and tibialis anterior muscles to sudden plantar flexion/inversion stress.

Adult↗