Biomedical subjects

K R Williams

Publications and source records attributed to K R Williams.

At least 19 recordsLinked to original sources

PubMed2006

Neural transplantation of human MSC and NT2 cells in the twitcher mouse model.

BACKGROUND: Accumulating evidence has demonstrated that the NT2 embryonal carcinoma cell line and multipotential stem cells found in BM, mesenchymal stromal cells (MSC), have the ability to differentiate into a wide variety of cell types. This study was designed to explore the efficacy of these two human stem cell types as a graft source for the treatment of demyelinating disorders such as Krabbe's disease and multiple sclerosis (MS). METHODS: We examined the engraftment and in vivo differentiation of adult MSC and NT2 cells after transplantation into two demyelinating environments, the neonatal and postnatal twitcher mouse brain. RESULTS: Both types of xenografts led to anatomical integration, without tumor formation, and remained viable in the normal and twitcher mouse brain, showing differentiation into neurons, astrocytes and oligodendrocytes. DISCUSSION: This study represents a platform for further stem cell transplantation studies in the twitcher model and potentially has important therapeutic implications.

Animals↗

PubMed2006

A numerical approach to resonance frequency analysis for the investigation of oral implant osseointegration.

Experimental devices based on vibration testing are employed as non-destructive procedures for evaluating implants osseointegration. Their behaviour was evaluated considering the outcome of numerical analysis. The purpose was to use the finite element method for assessing the ability of frequency analysis in detecting the degree of oral implant osseointegration. A three-dimensional model of a mandible was obtained from tomographic survey. A single implant was considered in canine region. Two configurations were analysed, with and without a mass linked to the implant as a cantilever, reproducing experimental devices. Simulation consisted of analysing the response to impulse forces for different osseointegration levels, thus evaluating the biomechanical efficiency of the implant-bone compound. A good correlation between frequency response and osseointegration level was obtained. This was carried out by providing an impulse excitation of the implant that resulted in a vibration pattern. Within the limit of finite element analysis, the outcomes showed that numerical investigation provides understanding the behaviour of testing devices based on frequency measurements, confirming the potential of vibrations technique as non-invasive analysis for osseointegration process.

Biomechanical Phenomena↗

PubMed2006

The Son-Rise Program intervention for autism: prerequisites for evaluation.

With increasing availability of interventions for children with autism, it is important that these are backed by rigorous evaluation data that have high levels of ecological validity. To achieve this, a key prerequisite for any evaluation is to gather data on typical consumers and typical implementation patterns of the intervention. This study collected such data longitudinally in relation to the Son-Rise Program, a home-based parent-run intervention for autism. Questionnaires and interview data on family demographics, implementation patterns, and perceived treatment fidelity were gathered three times over the course of a year from families who had attended a Son-Rise initial training course. Although it proved possible to produce a profile of intervention use, findings indicated that the programme is not always implemented as it is typically described in the literature. The study also highlighted methodological challenges likely to be encountered in any future evaluation of this and similar interventions for autism.

Autistic Disorder↗

PubMed2004

The effect of feedback training on lumbosacral compression during simulated occupational lifting.

This study measured the effect of a feedback training program on lumbar compression during simulated occupational lifting. Two distinct types of feedback were compared: real-time electromyographic feedback, vs. an acceleration index delivered verbally post-lift. Kinematic data were collected from 28 subjects during symmetrical sagittal plane lifts. Following a baseline session, two feedback training sessions were provided, with a 1-week interval between each session. A control group followed the same protocols, but without receiving feedback training. A post-training session, using protocols identical to the baseline session, was used to assess pre-to-post changes in the dependent variable: peak lumbosacral compression computed using a dynamic linked-segment model. All three groups showed reductions in peak compression from pre-to-post: on average the control group improved by 11.2%, the EMG group by 16.7%, and the acceleration group by 25.3%. The results revealed an interaction between the improvement and the group (p=0.023), and a difference between the improvement in the control group and that in the verbal acceleration feedback group (p<0.01). These reductions in lumbosacral compression persisted after a 7-day interval without feedback training, suggesting that this approach could provide sustained risk-reduction during manual materials handling.

Acceleration↗

PubMed2002

Multimodality radiotherapy and androgen ablation in the treatment of clinically localized prostate cancer: early results in high risk patients.

In patients presenting with clinically localized prostate cancer, the risk of biochemical failure increases significantly with higher Gleason scores, prostate specific antigen (PSA) levels, and clinical stages. Current surgical and radiotherapeutic approaches appear to offer limited success in patients with highly adverse prognostic factors. In an attempt to improve on these outcomes, we have combined external beam radiotherapy (EBRT) with a brachytherapy (BT) boost and neo adjuvant and adjuvant androgen ablation in a population at significant risk of biochemical failure. Here we present early biochemical progression data for this approach. From October 1997 to July 1999, 72 men with a serum PSA >or=10 ng/ml or Gleason score >or=7 or clinical stage >or=T2c (AJC/UICC 1992) underwent EBRT followed by palladium-103 BT. All patients underwent 8 months of combined androgen ablation with leuprolide and an oral antiandrogen beginning 3 months prior to initiation of EBRT. Patients were followed by PSA and digital rectal examination (DRE) at 3-month intervals and a chart review on all patients was carried out during July 2001. To allow comparisons to contemporary literature, Kaplan-Meier survival curves were generated utilizing three alternate definitions of biochemical recurrence: PSA >0.2 ng/ml, PSA >1.0 ng/ml, and the American Society for Therapeutic Radiology and Oncology (ASTRO) consensus definition of three consecutive rising PSAs. Our results indicate that when PSA >0.2 ng/ml was used to define biochemical progression, 88% (95% CI 80-97) of patients remained free of disease at 24 months. When PSA >1.0 ng/ml was used, 97% (CI 92-100) of patients remained disease free at 24 months. ASTRO criteria yielded 90% (CI 82-98) recurrence-free survival at 24 months. In conclusion, this very early report indicates that in patients who are at increased risk of biochemical failure, EBRT with a BT boost in conjunction with short-term androgen ablation offers potentially superior biochemical disease-free survival to contemporary alternative approaches in the literature. Clearly, longer follow-up is required to confirm the durability of this approach.

Aged↗

PubMed2001

Correcting out-of-plane errors in two-dimensional imaging using nonimage-related information.

Two-dimensional imaging with a single camera assumes that the motion occurs in a calibrated plane perpendicular to the camera axis. It is well known that kinematic errors result if the object fails to remain in this plane and that if both the distance to the calibration plane from the camera and the distance out-of-plane are known, an analytical correction for the out-of-plane error can be made. Less well appreciated is that out-of-plane distance can frequently be acquired from other, nonimage-related information. In the two examples given, the mediolateral center of pressure coordinate of the foot measured from a force plate and the measured landing point of a shot put throw were used. In both cases, the resulting out-of-plane correction improved the accuracy of the 2-D kinematic data dramatically. These examples also demonstrate that the use of nonimage-related data can increase the accuracy of kinematic data without an increase in the complexity of the experiment.

Diagnostic Errors↗

PubMed2001

Head injury and alexithymia: implications for family practice care.

BACKGROUND: Alexithymia, a deficit in emotional information processing, and a history of head injury have both been found to be related to high rates of psychosomatic illness, substance abuse, depression, and utilization of primary care services. To date, no study has examined the potential comorbidity of alexithymia and head injury in a family practice setting, a necessary step in evaluating the aetiologic role of head injury in the development of alexithymia. The goals of this study are to establish prevalence of head injury and alexithymia in a family practice setting and to evaluate the relation, if present, between the two. METHODS: Patients (n =135) of a family practice residency facility were screened using the Traumatic Brain Injury Questionnaire and the Toronto Alexithymia Scale-20. RESULTS: Forty-nine per cent of the participants reported a history of head injury and 18% were alexithymic. Those with a history of head injury had significantly higher scores of alexithymia. Chi-square analysis indicated a relation between head injury and alexithymia. CONCLUSIONS: The high rates of self-reported history of head injury in family practice settings, particularly in the context of alexithymia, may adversely affect a physician's ability to care for these patients. Increasing physicians' awareness of head injury and the potential mediating role of alexithymia in medical and psychological illness may facilitate effective diagnosis and patient-physician communication.

Adolescent↗

PubMed2000

PRMT1 is the predominant type I protein arginine methyltransferase in mammalian cells.

Type I protein arginine methyltransferases catalyze the formation of asymmetric omega-N(G),N(G)-dimethylarginine residues by transferring methyl groups from S-adenosyl-L-methionine to guanidino groups of arginine residues in a variety of eucaryotic proteins. The predominant type I enzyme activity is found in mammalian cells as a high molecular weight complex (300-400 kDa). In a previous study, this protein arginine methyltransferase activity was identified as an additional activity of 10-formyltetrahydrofolate dehydrogenase (FDH) protein. However, immunodepletion of FDH activity in RAT1 cells and in murine tissue extracts with antibody to FDH does not diminish type I methyltransferase activity toward the methyl-accepting substrates glutathione S-transferase fibrillarin glycine arginine domain fusion protein or heterogeneous nuclear ribonucleoprotein A1. Similarly, immunodepletion with anti-FDH antibody does not remove the endogenous methylating activity for hypomethylated proteins present in extracts from adenosine dialdehyde-treated RAT1 cells. In contrast, anti-PRMT1 antibody can remove PRMT1 activity from RAT1 extracts, murine tissue extracts, and purified rat liver FDH preparations. Tissue extracts from FDH(+/+), FDH(+/-), and FDH(-/-) mice have similar protein arginine methyltransferase activities but high, intermediate, and undetectable FDH activities, respectively. Recombinant glutathione S-transferase-PRMT1, but not purified FDH, can be cross-linked to the methyl-donor substrate S-adenosyl-L-methionine. We conclude that PRMT1 contributes the major type I protein arginine methyltransferase enzyme activity present in mammalian cells and tissues.

Animals↗

PubMed2000

Elevated levels of Ca(II) modulate the activity and inhibition of serine proteases: implication in the mechanism of apoptosis.

Elevated levels of intracellular Ca(II) are a prominent feature of apoptosis, a natural form of cell death involved in many physiological and pathological processes. Serine proteases play crucial roles in apoptosis and have been implicated in the genomic DNA degradation and the massive protein degradation that occur during apoptosis. In this study, the effects of the elevated level of Ca(II) on the activity and inhibition of serine proteases were examined by spectrophotometric methods. The effects of the elevated levels of Ca(II), Mg(II), K(I), and Na(I) on the activity and inactivation of three representative members of serine proteases were determined. The level of serine protease activity in CEM-C7-14 leukemic cells was also evaluated in the presence and absence of dexamethasone-induced apoptosis, and also in the presence of A23187, a Ca(II)-ionophore. Among the four metal-ions studied, only Ca(II) was found to significantly enhance the activity of mammalian serine proteases. Ca(II) was also found to significantly protect the enzymes from inhibition, while the other three metal-ions showed no significant effect on the inactivation of the enzymes. Compared to the control sample, the enzymic activity was found to be higher during apoptosis, and in the presence of the Ca(II)-ionophore. Results of this study indicate that Ca(II) can significantly enhance the catalytic efficiency of serine proteases during apoptosis.

Apoptosis↗

PubMed1999

Identification of the RNA binding domain of T4 RegA protein by structure-based mutagenesis.

The T4 translational repressor RegA protein folds into two structural domains, as revealed by the crystal structure (Kang, C.-H. , Chan, R., Berger, I., Lockshin, C., Green, L., Gold, L., and Rich, A. (1995) Science 268, 1170-1173). Domain I of the RegA protein contains a four-stranded beta-sheet and two alpha-helices. Domain II contains a four-stranded beta-sheet and an unusual 3/10 helix. Since beta-sheet residues play a role in a number of protein-RNA interactions, one or both of the beta-sheet regions in RegA protein may be involved in RNA binding. To test this possibility, mutagenesis of residues on both beta-sheets was performed, and the effects on the RNA binding affinities of RegA protein were measured. Additional sites for mutagenesis were selected from molecular modeling of RegA protein. The RNA binding affinities of three purified mutant RegA proteins were evaluated by fluorescence quenching equilibrium binding assays. The activities of the remainder of the mutant proteins were evaluated by quantitative RNA gel mobility shift assays using lysed cell supernatants. The results of this mutagenesis study ruled out the participation of beta-sheet residues. Instead, the RNA binding site was found to be a surface pocket formed by residues on two loops and an alpha-helix. Thus, RegA protein appears to use a unique structural motif in binding RNA, which may be related to its unusual RNA recognition properties.

Bacteriophage T4↗

PubMed1998

Identification of protein-arginine N-methyltransferase as 10-formyltetrahydrofolate dehydrogenase.

S-Adenosylmethionine:protein-arginine N-methyltransferase (EC 2.1.1. 23; protein methylase I) transfers the methyl group of S-adenosyl-L-methionine to an arginine residue of a protein substrate. The homogeneous liver protein methylase I was subjected to tryptic digestion followed by reverse phase high performance liquid chromatography (HPLC) separation and either "on-line" mass spectrometric fragmentation or "off-line" Edman sequencing of selected fractions. Data base searching of both the mass spectrometric and Edman sequencing data from several peptides identified the protein methylase as 10-formyltetrahydrofolate dehydrogenase (EC 1.5.1.6; Cook, R. J., Lloyd, R. S., and Wagner, C. (1991) J. Biol. Chem. 266, 4965-4973; Swiss accession number). This identification was confirmed by comparative HPLC tryptic peptide mapping and affinity chromatography of the methylase on the 5-formyltetrahydrofolate-Sepharose affinity gel used to purify the dehydrogenase. The purified rat liver methylase had approximately 33% of the 10-formyltetrahydrofolate dehydrogenase and 36% of the aldehyde dehydrogenase activity as compared with the recombinant dehydrogenase, which also had protein methylase I activity. Polyclonal antibodies against recombinant dehydrogenase reacted with protein methylase I purified either by polyacrylamide gel electrophoresis or 5-formyltetrahydrofolate affinity chromatography. In each instance there was only a single immunoreactive band at a molecular weight of approximately 106,000. Together, these results confirm the co-identity of protein-arginine methyltransferase and 10-formyltetrahydrofolate dehydrogenase.

Amino Acid Sequence↗

PubMed1998

Use of liquid chromatography-electrospray ionization-tandem mass spectrometry (LC-ESI-MS/MS) for routine identification of enzymatically digested proteins separated by sodium dodecyl sulfate-polyacrylamide gel electrophoresis.

Automated liquid chromatography-electrospray ionization-tandem mass spectrometry (LC-ESI-MS/MS) analysis of >100 tryptic digests carried out on sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) separated, Coomassie Blue-stained proteins that were prepared by >50 different laboratories demonstrates that a commercial electrospray/quadrupole ion trap mass spectrometer and the tandem mass correlation algorithm developed by Eng et al. (Am. Soc. Mass Spectrom. 1994, 5, 976-989) provide an extremely robust and facile approach to routine protein identification. By requiring a minimum of two significant matches to peptides that would be predicted to be produced by the protease that was used, low pmol levels of proteins can be identified with high confidence while minimizing the probability of identifying the protease itself and/or the ubiquitous contaminant, keratin. Hence, in only 7% of the digests analyzed was keratin identified and in only 5% of the digests analyzed was the protease itself identified. In contrast, 58% of the analyzed samples were identified and, in many instances, multiple proteins were identified in the same sample. Although the median amount of digest analyzed was 6.1 pmol, the limit of sensitivity (as the instrument is configured with a flow rate of 4 microL/min) appears to be at the 500 fmol level. Since one of the primary reasons for not identifying a sample is that its sequence is not yet in the database searched, the utility of an LC MS/MS approach to protein identification will certainly increase in the future as the sequences of more genomes are completed.

Chromatography, High Pressure Liquid↗

PubMed1998

Uptake and internalization of exogenous apolipoprotein E3 by cultured human central nervous system neurons.

Apolipoprotein E (apoE) has been confirmed as a risk factor for late-onset Alzheimer's disease (AD) and is associated with neurofibrillary tangles and senile plaques, the microscopic pathological characteristics of AD. There has been no direct evidence that human central nervous system neurons can take up and internalize exogenous apoE, which may be important in order for apoE to be involved in the development of the disease. This paper demonstrates by immunohistochemistry and confocal microscopy that cultured human brain neurons can take up and internalize exogenous recombinant human apoE3. We confirm that neurons express the low-density lipoprotein receptor-related protein (LRP) but do not express the low-density lipoprotein receptor. We also demonstrate that the LRP mediates the neuronal uptake of apoE.

Apolipoprotein E3↗

PubMed1998

Design of prosthetic cantilever bridgework supported by osseointegrated implants using the finite element method.

OBJECTIVES: The aim of the present work was to establish a design procedure for fixed metal prostheses supported by osseointegrated implants in order to prevent permanent deformation and hence failure following loading. Previously, the cantilever cross-sectional shape in the buccal lingual plane has been based on clinical experience and subjectivity. METHODS: This work has relied on the use of linear elastic finite element analysis in order to generate a maximum effective stress at which permanent deformation commences on loading. A number of different cross-sectional shapes were investigated, both of conventional design as well as new innovative possibilities. Both straight and curved cantilever beams 26 mm long were examined. RESULTS: The design failure chosen was based on a von Mises plastic collapse principle by comparing the calculated effective stresses with the yield stress of the metal in simple tension. It was found that the "L" shaped design was more rigid than other designs for a given mass, while a framework based on an open "I" section offers good possibilities particularly when used as curved shapes. SIGNIFICANCE: Assuming a failure criterion based on the von Mises principle, then "L" shaped Co/Cr or stainless steel frameworks, typically 26 mm of cantilever span, undergo permanent deformation at end loadings between 130 and 140 N depending on section curvature. Since it is known biting loads can exceed these values, good design is critical if such failures are to be avoided.

Dental Alloys↗

PubMed1997

Identification of N(G)-methylarginine residues in human heterogeneous RNP protein A1: Phe/Gly-Gly-Gly-Arg-Gly-Gly-Gly/Phe is a preferred recognition motif.

Three sites of N(G),N(G)-arginine methylation have been located at residues 205, 217, and 224 in the glycine-rich, COOH-terminal one-third of the HeLa A1 heterogeneous ribonucleoprotein. Together with the previously determined dimethylated arginine at position 193 [Williams et al., (1985) Proc. Natl. Acad. Sci. U.S.A. 82, 5666-5670], it is evident that all four sites fall within a span of sequence between residues 190 and 233 that contains multiple Arg-Gly-(Gly) sequences interspersed with phenylalanine residues. These RGG boxes have been postulated to represent an RNA binding motif [Kiledjian and Dreyfuss (1992) EMBO J. 11, 2655-2664]. Dimethylation of HeLa A1 appears to be quantitative at each of the four positions. Arginines 205 and 224 have been methylated in vitro by a nuclear protein arginine methyltransferase using recombinant (unmethylated) A1 as substrate. This suggests A1 may be an in vivo substrate for this enzyme. Examination of sequences surrounding the sites of methylation in A1 along with a compilation from the literature of sites that have been identified in other nuclear RNA binding proteins suggests a methylase-preferred recognition sequence of Phe/Gly-Gly-Gly-Arg-Gly-Gly-Gly/Phe, with the COOH-terminal flanking glycine being obligatory. Taken together with data in the literature, identification of the sites of A1 arginine methylation strongly suggests a role for this modification in modulating the interaction of A1 with nucleic acids.

Amino Acid Sequence↗

PubMed1997

Two two-gene macronuclear chromosomes of the hypotrichous ciliates Oxytricha fallax and O. trifallax generated by alternative processing of the 81 locus.

We describe the first know macronuclear chromosomes that carry more than one gene in hypotrichous ciliated protozoa. These 4.9- and 2.8-kbp chromosomes each consist almost exclusively of two protein-coding genes, which are conserved and transcribed. The two chromosomes share a common region that consists of a gene that is a member of the family of mitochondrial solute carrier genes (CR-MSC; [Williams and Herrick (1991): Nucleic Acids Res 19:4717-4724]. Each chromosome also carries another gene appended to its common region: The 4.9-kbp chromosome also carries a gene that encodes a protein that is rich in glutamine and charged amino acids and bears regions of heptad repeats characteristic of coiled-coils. Its function is unknown. The second gene of the 2.8 kbp chromosome is a mitochondrial solute carrier gene (LA-MSC); thus, the 2.8-kbp chromosomes consists of two mitochondrial solute carrier paralogs. Phylogenetic analysis indicates that the two genes were duplicated before ciliates diverged from the main eukaryotic lineage and were subsequently juxtaposed. The CR- and LA-MSC genes are each interrupted by three introns. The introns are not in homologous positions, suggesting that they may have originated from multiple group II intron transpositions. These chromosomes and their genes are encoded in the Oxytricha germline by the 81 locus. This locus is alternatively processed to generate a nested set of three macronuclear chromosomes, the 4.9- and 2.8-kbp chromosomes and a third (1.6 kbp) which consists almost exclusively of the shared common gene, CR-MSC. Such alternative processing is common in macronuclear development of O. fallax [Cartinhour and Herrick (1984): Mol Cell Biol 4:931-938]. Possible functions for alternative processing are considered; e.g., it may serve to physically link genes to allow co-regulation or co-replication by a common cis-acting sequence.

Animals↗

PubMed1997

Apolipoprotein E uptake and low-density lipoprotein receptor-related protein expression by the NTera2/D1 cell line: a cell culture model of relevance for late-onset Alzheimer's disease.

Apolipoprotein E has been shown to be a risk factor for late-onset Alzheimer's disease, with the apolipoprotein epsilon 4 allele conferring the risk. Apolipoprotein E is found in neurofibrillary tangles and senile plaques, the pathological characteristics of Alzheimer's disease. To date there is no direct evidence that human neurons can take up exogenous apolipoprotein E, which is necessary if apolipoprotein E is involved in the formation of neurofibrillary tangles. To examine apolipoprotein E uptake we employed the human NTera2/D1 cell line, which can be induced by retinoic acid to differentiate into postmitotic NTera2-N neurons, which have the characteristics and morphology of human central nervous system neurons. We defined the cell line as genotype apolipoprotein epsilon 3/3 and demonstrated that the cells do not synthesize apolipoprotein E but can take up and internalize exogenous recombinant apolipoprotein E3. We also confirmed the expression of the low-density lipoprotein receptor-related protein, a known receptor for apolipoprotein E. The NTera2/D1 cell line therefore provides a useful human cell model for examining the effects of other apolipoprotein E isoforms with a view to defining intraneuronal interactions of apolipoprotein E.

Alzheimer Disease↗

PubMed1997

Enzymatic cleavage and HPLC peptide mapping of proteins.

Detailed procedures are described for successfully digesting reasonably small quantities (i.e., usually > 10 pmol) of proteins with a variety of proteases and for then isolating the resulting peptides by reverse-phase HPLC. Since sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) appears to be the current method of choice for final purification of proteins for structural analysis, special attention is given to carrying out in-gel proteolytic digests on SDS-PAGE-separated proteins that have usually been stained with Coomassie Blue. A compilation of data from nearly 200 "unknown" samples is used to help provide realistic expectations with respect to the results that are likely to be obtained from carrying out in-gel proteolytic digests on large numbers of proteins.

Amino Acids↗