Biomedical subjects

R Allen

Publications and source records attributed to R Allen.

At least 37 records · Page 2Linked to original sources

PubMed2003

A profile of putative parasitism genes expressed in the esophageal gland cells of the root-knot nematode Meloidogyne incognita.

Identifying parasitism genes encoding proteins secreted from a nematode's esophageal gland cells and injected through its stylet into plant tissue is the key to understanding the molecular basis of nematode parasitism of plants. Meloidogyne incognita parasitism genes were cloned by microaspirating the cytoplasm from the esophageal gland cells of different parasitic stages to provide mRNA to create a gland cell-specific cDNA library by long-distance reverse-transcriptase polymerase chain reaction. Of 2,452 cDNA clones sequenced, deduced protein sequences of 185 cDNAs had a signal peptide for secretion and, thus, could have a role in root-knot nematode parasitism of plants. High-throughput in situ hybridization with cDNA clones encoding signal peptides resulted in probes of 37 unique clones specifically hybridizing to transcripts accumulating within the subventral (13 clones) or dorsal (24 clones) esophageal gland cells of M. incognita. In BLASTP analyses, 73% of the predicted proteins were novel proteins. Those with similarities to known proteins included a pectate lyase, acid phosphatase, and hypothetical proteins from other organisms. Our cell-specific analysis of genes encoding secretory proteins provided, for the first time, a profile of putative parasitism genes expressed in the M. incognita esophageal gland cells throughout the parasitic cycle.

Animals↗

PubMed2003

The parasitome of the phytonematode Heterodera glycines.

Parasitism genes expressed in the esophageal gland cells of phytonematodes encode secretions that control the complex process of plant parasitism. In the soybean cyst nematode, Heterodera glycines, the parasitome, i.e., the secreted products of parasitism genes, facilitate nematode migration in soybean roots and mediate the modification of root cells into elaborate feeding cells required to support the growth and development of the nematode. With very few exceptions, the identities of these secretions are unknown, and the mechanisms of cyst nematode parasitism, therefore, remain obscure. The most direct and efficient approach for cloning parasitism genes and rapidly advancing our understanding of the molecular interactions during nematode parasitism of plants is to create gland cell-specific cDNA libraries using cytoplasm microaspirated from the esophageal gland cells of various parasitic stages. By combining expressed sequence tag analysis of a gland cell cDNA library with high throughput in situ expression localization of clones encoding secretory proteins, we obtained the first comprehensive parasitome profile for a parasitic nematode. We identified 51 new H. glycines gland-expressed candidate parasitism genes, of which 38 genes constitute completely novel sequences. Individual parasitome members showed distinct gland cell expression patterns throughout the parasitic cycle. The parasitome complexity discovered paints a more elaborate picture of host cellular events under specific control by the nematode parasite than previously hypothesized.

Animals↗

PubMed2003

Variation in the DCP1 gene, encoding the angiotensin converting enzyme ACE, is not associated with increased susceptibility to Alzheimer's disease.

OBJECTIVES: To attempt to replicate previous reports that polymorphic variation in the DCP1 gene causes increased susceptibility to the development of Alzheimer's disease, either on its own or in interaction with the effects of the gene for apolipoprotein E (APOE). METHOD: Subjects older than 65 years of age consisting of 81 dementia patients diagnosed as having possible or probable Alzheimer's disease and 68 controls were obtained from Camden, Islington and Harlow psychiatric services. Subjects were genotyped for APOE alleles e2, e3 and e4, and the common insertion/deletion polymorphisms for DCP1* I/D were genotyped. RESULTS: There was no statistically significant difference in the frequency of the DCP1* insertion/deletion alleles between the cases and controls (X2 =0.04, 1 degree of freedom, not significant). When subjects were subdivided according to whether they possessed at least one copy of the APOE e4 allele, there were still no differences in DCP1 allele frequencies between cases and controls. CONCLUSIONS: Further research is needed to elucidate any role that the DCP1 polymorphism may play in relation to Alzheimer's disease. Previous studies may be false positive, or inconsistency in replication may be due to heterogeneity.

Aged↗

PubMed2002

Analysis of dynamic cerebral autoregulation using an ARX model based on arterial blood pressure and middle cerebral artery velocity simulation.

The study aimed to model the cerebrovascular system, using a linear ARX model based on data simulated by a comprehensive physiological model, and to assess the range of applicability of linear parametric models. Arterial blood pressure (ABP) and middle cerebral arterial blood flow velocity (MCAV) were measured from 11 subjects non-invasively, following step changes in ABP, using the thigh cuff technique. By optimising parameters associated with autoregulation, using a non-linear optimisation technique, the physiological model showed a good performance (r=0.83+/-0.14) in fitting MCAV. An additional five sets of measured ABP of length 236+/-154 s were acquired from a subject at rest. These were normalised and rescaled to coefficients of variation (CV=SD/mean) of 2% and 10% for model comparisons. Randomly generated Gaussian noise with standard deviation (SD) from 1% to 5% was added to both ABP and physiologically simulated MCAV (SMCAV), with 'normal' and 'impaired' cerebral autoregulation, to simulate the real measurement conditions. ABP and SMCAV were fitted by ARX modelling, and cerebral autoregulation was quantified by a 5 s recovery percentage R5% of the step responses of the ARX models. The study suggests that cerebral autoregulation can be assessed by computing the R5% of the step response of an ARX model of appropriate order, even when measurement noise is considerable.

Blood Flow Velocity↗

PubMed2002

Characterisation and developmental expression of a chitinase gene in Heterodera glycines.

A chitinase full-length cDNA (designated Hg-chi-1) was isolated from a Heterodera glycines oesophageal gland cell-specific long-distance PCR cDNA library. The cDNA hybridised to genomic DNA of H. glycines in Southern blots. The Hg-chi-1 cDNA contained an open reading frame encoding 350 amino acids with the first 23 amino acids being a putative signal peptide for secretion. Hg-CHI-1 contained a chitinase 18 family catalytic domain, and chitinolytic activity of recombinant Hg-CHI-1 was confirmed in glycol-chitin substrate gel electrophoresis. In situ mRNA hybridisation analyses showed that transcripts of Hg-chi-1 accumulated specifically in the subventral oesophageal gland cells of parasitic stages of H. glycines, but Hg-chi-1 expression was not detected in eggs or hatched pre-parasitic second-stage juveniles, suggesting that this chitinase does not have a role in egg hatching of H. glycines. The biological function of Hg-CHI-1 in H. glycines remains to be determined.

Amino Acid Sequence↗

PubMed2002

Transferring people safely with manual handling equipment.

OBJECTIVE: To determine whether transferring equipment designed to assist a carer when moving someone who is able to take some weight through their legs is likely to affect the risk of back problems in the carer. DESIGN: Twelve pieces of equipment were tested by nurses transferring patients from commode to wheelchair and vice versa, and from wheelchair to bed and vice versa. Video recordings were taken of each transfer and freeze-frame pictures at the moment of greatest load were analysed. Compressive disc force was deduced, using a biomechanical model, from the weights of the patient and nurse and measurements of anatomical distances and angles. SETTING: The Sir Walter Puckey Gait Laboratory, in the Rehabilitation Research Unit, University of Southampton. SUBJECTS: Six female trained nurses with no recent history of hernia, back pain or pregnancy during the previous six months were recruited to use the equipment. Two female patients were chosen from those volunteering and screened for stroke, confusion and unusual footwear. The patients were able to partially weight-bear and were used to being transferred. RESULTS: The results indicate that the critical value of 3.4 kN at the L5/S1 disc (specified by the US National Institute for Occupational Safety and Health) was not exceeded when using transferring equipment. CONCLUSION: In this study, loading on the spine during transferring tasks with or without equipment was not considered harmful when good technique was employed.

Back Injuries↗

PubMed2002

Non-invasive assessment of intracranial compliance using a new 2-D "transit time" vs "frequency centroid" map.

The objective of this research was to develop a new static two dimensional graphic display indicating changes to intracranial compliance using non invasive ultrasonic Doppler measurements of the Middle Cerebral Artery (MCA) velocity and Arterial Blood Pressure (ABP). ABP and MCA velocity were measured in a volunteer patient study and the results for hypo-, normo- and hyper-capnia, conditions were recorded. Cross-correlation analysis between ABP and MCA velocity predicted a change in "transit time" between the two parameters and a Fourier Transform analysis of the MCA velocity data predicted a change in "frequency centroid" over the 0 to 10 Hz range indicating change with intracranial compliance. The results for the hyper-capnia condition were: "Transit Time"--0 ms, "Frequency Centroid"--1.9 Hz, for the normo-capnia condition: "Transit Time"--18 ms, "Frequency Centroid"--2.5 Hz, for the hypo-capnia condition: "Transit Time"--38 ms, "Frequency Centroid"--3.1 Hz. Plotting the results on a graph with "Frequency Centroid" as the vertical axis and "Transit Time" as the horizontal axis yields a locus possibly indicating a change to intracranial compliance.

Blood Flow Velocity↗

PubMed2001

Evolution and transmission of stable CTL escape mutations in HIV infection.

Increasing evidence indicates that potent anti-HIV-1 activity is mediated by cytotoxic T lymphocytes (CTLs); however, the effects of this immune pressure on viral transmission and evolution have not been determined. Here we investigate mother-child transmission in the setting of human leukocyte antigen (HLA)-B27 expression, selected for analysis because it is associated with prolonged immune containment in adult infection. In adults, mutations in a dominant and highly conserved B27-restricted Gag CTL epitope lead to loss of recognition and disease progression. In mothers expressing HLA-B27 who transmit HIV-1 perinatally, we document transmission of viruses encoding CTL escape variants in this dominant Gag epitope that no longer bind to B27. Their infected infants target an otherwise subdominant B27-restricted epitope and fail to contain HIV replication. These CTL escape variants remain stable without reversion in the absence of the evolutionary pressure that originally selected the mutation. These data suggest that CTL escape mutations in epitopes associated with suppression of viraemia will accumulate as the epidemic progresses, and therefore have important implications for vaccine design.

Adult↗

PubMed2001

The limitations of orthographic analogy in early reading development: performance on the clue-word task depends on phonological priming and elementary decoding skill, not the use of orthographic analogy.

Two experiments investigated the mechanisms underlying analogical transfer in the clue-word reading task developed by Goswami and her colleagues. Across both experiments, an equivalent number of "analogy" responses were made regardless of whether the clue word was seen or just heard. In addition, the number of "analogy" responses to words sharing both orthographic and phonological overlap with the clue words was no greater than that shown to words sharing only pronunciations. These results provide no evidence for the view that beginning readers make genuine orthographic-based analogies. Instead, the findings are interpreted within a framework in which phonological priming, in combination with the children's own partial decoding attempts based on limited orthographic knowledge, account for their performance on the clue-word task. It is concluded that the extent to which beginning readers make orthographic analogies is overestimated and as a consequence, theories that emphasize the importance of orthographic analogy as a mechanism driving the development of early reading skills need to be questioned.

Child↗

PubMed2001

Automatic recognition of vertebral landmarks in fluoroscopic sequences for analysis of intervertebral kinematics.

Intervertebral kinematics closely relates to the functionality of the spinal segments. Direct measurement of the intervertebral kinematics in vivo is very problematic. The use of a fluoroscopic device can provide continuous screening of the lumbar tract during patient spontaneous motion, with an acceptable, low X-ray dose. The kinematic analysis is intended to be limited to planar motion. Kinematic parameters are computed from vertebral landmarks on each frame of the image sequence. Landmarks are normally selected manually in spite of the fact that this is subjective, tedious to perform and regarded as one of the major contributors to errors in the computed kinematic parameters. The aim of this work is to present an innovative method for the automatic recognition of vertebral landmarks throughout a fluoroscopic image sequence to provide an objective and more precise quantification of intervertebral kinematics. The recognition procedure is based upon comparing vertebral features in two adjacent frames by means of a cross-correlation index, which is also robust despite the low signal-to-noise ratio of the lumbar fluoroscopic images. To provide a quantitative assessment of this method a calibration model was used which consisted of two lumbar vertebrae linked by a universal joint. The reliability and accuracy of the kinematic measurements have been investigated. The errors are of the order of a millimetre for the localisation of the intervertebral centre of rotation and tenths of a degree for the intervertebral angle. Error analysis suggests that this method improves the accuracy of the intervertebral kinematic calculations and has the potential to automate the selection of anatomical landmarks.

Calibration↗

PubMed2001

Computer visualisation of the moving human lumbar spine.

Disorders of the spine which lead to back pain are often mechanical in origin and, despite extensive research, diagnosis of the underlying cause remains problematical, yet back pain is one of the most common rheumatological symptoms presented to the general practitioner. Diagnosis must frequently be based upon evidence gathered at the segmental level which invariably means that imaging is used in the process. In addition, surgical fixation is increasingly used when the spinal column is considered to exhibit instability. A solid model of the spine creates the possibility of visualising spine motion, of assessing the effects of loading of the spinal column in conjunction with finite element analysis to investigate the consequences of vertebral fusion, and of planning surgical intervention. Such a model could also be valuable in medical education and for demonstrating spine motion to a patient to highlight abnormalities or the effects of treatment. This paper describes a three-dimensional visualisation of the human lumbar spine which runs on a personal computer operating under the Windows environment. The user interface enables the clinician to select the viewpoint for the spine model to allow the motion to be studied from different angles. Motion data are currently acquired from fluoroscopic image sequences but the model could be used to display data from different imaging modalities when they are developed sufficiently for spine motion studies.

Computer Simulation↗

PubMed2001

Molecular characterisation and expression of two venom allergen-like protein genes in Heterodera glycines.

Secretory proteins encoded by genes expressed in the oesophageal gland cells of plant-parasitic nematodes have key roles in nematode parasitism of plants. Two venom allergen-like protein cDNAs (designated hg-vap-1 and hg-vap-2)were isolated from Heterodera glycines gland cell cDNA libraries. Both cDNAs hybridised to genomic DNA of H. glycines in Southern blots. The hg-vap-1 cDNA contained an open reading frame encoding 215 amino acids with the first 25 amino acids being a putative secretion signal. The hg-vap-2 cDNA contained an open reading frame encoding 212 amino acids with the first 19 amino acids being a putative secretion signal. Genes of hg-vap-1 and hg-vap-2 contained four introns, which ranged in size from 44 to 574 bp, and five exons ranging in size from 43 to 279 bp. In situ hybridisation analyses showed that mRNAs of both vap genes accumulated specifically in the subventral gland cells of H. glycines during parasitism. The gland cell-specific expression and presence of predicted secretion signal peptides in both VAPs suggest that these proteins are secreted from the nematode and may play a role in the infection of host plants by this parasite.

Allergens↗

PubMed2001

Use of an immunoassay as a means to detect polychlorinated biphenyls in animal fat.

In this paper we describe the validation and utilization of the Hybrinzme DELFIA immunoassay for detecting polychlorinated biphenyls (PCBs) in animal fat. The immunoassay incorporates a rapid sample processing protocol that has been optimized to detect concentrations of PCBs in animal fat at or above 200 ng/g. The limit of detection of the assay was less than 50 ng/g. When the action level for the DELFIA assay was set at 100 ng/g to detect samples having 200 ng/g or more PCBs, the false negative rate was estimated at 0.2%. The false positive rate depends on the concentration of PCBs in the sample population and was estimated at 4% and 7% for samples having 10 ng/g and 20 ng/g PCBs, respectively. By utilizing the DELFIA assay system to select for positive samples and GC/MS analysis for confirmation analysis, an accurate and cost-effective programme has been established for the high throughput detection of PCBs in animal products.

Adipose Tissue↗

PubMed2001

A cost-effective weighing chamber for particulate matter filters.

Particulate matter (PM) is a ubiquitous air pollutant that has been receiving increasing attention in recent years due in part to the association between PM and a number of adverse health outcomes, including mortality and increases in emergency room visits and respiratory symptoms, as well as exacerbation of asthma and decrements in lung function. As a result, the ability to accurately sample ambient PM has become important, both to researchers and to regulatory agencies. The federal reference method for the determination of fine PM as PM2.5 in the atmosphere recommends that particle-sampling filters be conditioned and weighed in an environment with constant temperature and relative humidity (RH). It is also recommended that vibration, electrostatic charges, and contamination of the filters from laboratory air be minimized to reduce variability in filter weight measurements. These controls have typically been maintained in small, environmentally controlled "cleanrooms." As an alternative to constructing an elaborate cleanroom, we have designed, and presented in this paper, an inexpensive weighing chamber to maintain the necessary level of humidity control.

Air Pollutants↗

PubMed2001

Protecting cotton photosynthesis during moderate chilling at high light intensity by increasing chloroplastic antioxidant enzyme activity.

This study examined the effect of increasing chloroplastic superoxide dismutase (SOD), ascorbate peroxidase (APX), or glutathione reductase (GR) activity via plant transformation of cotton on the initial recovery of photosynthesis following exposures to 10 degrees C and high photon flux density (PFD). Growing wild-type or non-expressing segregate plants (controls) and transformants at two PFDs (600 micromol m(-2) s(-1) and full sun) resulted in a range of total antioxidant enzyme activities. Total SOD activities above that for control leaves grown in full sun did not substantially improve the recoveries of CO(2)-saturated photosynthesis, especially for stress treatments lasting more than 1 h, while elevated APX or GR activity did improve recoveries after 1-3 h of the chilling treatment. No synergistic effects were noted when the activities of more than one antioxidant enzyme were elevated in transgenic hybrids. Although these results suggest that the protection of photosynthesis can be realized by reducing either superoxide or H(2)O(2) levels, thereby reducing the possibility of hydroxyl radical formation, the situation is complicated, since elevated APX or GR activity can improve recoveries even when additional SOD activity has no effect. In conclusion, to enhance the protection of photosynthesis using stroma-targeted antioxidant enzymes, enhancing metabolism associated with H(2)O(2) is more effective than enhancing the capacity for superoxide scavenging. Although small, the improvement in the protection of photosynthetic capacity may be sufficient to improve cotton yield in temperate regions with large diurnal temperature fluctuations.

Antioxidants↗

PubMed2001

Identification of putative parasitism genes expressed in the esophageal gland cells of the soybean cyst nematode Heterodera glycines.

Cloning parasitism genes encoding secretory proteins expressed in the esophageal gland cells is the key to understanding the molecular basis of nematode parasitism of plants. Suppression subtractive hybridization (SSH) with the microaspirated contents from Heterodera glycines esophageal gland cells and intestinal region was used to isolate genes expressed preferentially in the gland cells of parasitic stages. Twenty-three unique cDNA sequences from a SSH cDNA library were identified and hybridized to the genomic DNA of H. glycines in Southern blots. Full-length cDNAs of 21 clones were obtained by screening a gland-cell long-distance polymerase chain reaction cDNA library. Deduced proteins of 10 clones were preceded by a signal peptide for secretion, and PSORT II computer analysis predicted eight proteins as extracellular, one as nuclear, and one as plasmalemma localized. In situ hybridization showed that four of the predicted extracellular clones were expressed specifically in the dorsal gland cell, one in the subventral gland cells, and three in the intestine in H. glycines. The predicted nuclear clone and the plasmalemma-localized clone were expressed in the subventral gland cells and the dorsal gland cell, respectively. SSH is an efficient method for cloning putative parasitism genes encoding esophageal gland cell secretory proteins that may have a role in H. glycines parasitism of soybean.

Animals↗

PubMed2001

Signal peptide-selection of cDNA cloned directly from the esophageal gland cells of the soybean cyst nematode Heterodera glycines.

Secretions from the esophageal gland cells of plant-parasitic nematodes play critical roles in the nematode-parasitic cycle. A novel method to isolate cDNA encoding putative nematode secretory proteins was developed that utilizes mRNA for reverse transcription-polymerase chain reaction derived from microaspiration of the esophageal gland cell contents of parasitic stages of the soybean cyst nematode Heterodera glycines. The resulting H. glycines gland cell cDNA was cloned into the pRK18 vector, and plasmid DNA was transformed into a mutated yeast host for specific selection of cDNA inserts that encode proteins with functional signal peptides. Of the 223 cDNA clones recovered from selection in yeast, 97% of the clones encoded a predicted signal peptide. Fourteen unique cDNA clones hybridized to genomic DNA of H. glycines on Southern blots and, among them, nine cDNA clones encoded putative extracellular proteins, as predicted by PSORT II computer analysis. Four cDNA clones hybridized to transcripts within the dorsal esophageal gland cell of parasitic stages of H. glycines, and in situ hybridization within H. glycines was not detected for eight cDNA clones. The protocol provides a direct means to isolate potential plant-parasitic nematode esophageal gland secretory protein genes.

Animals↗

PubMed2001

The feasibility of maximum length sequences to reduce acquisition time of the middle latency response.

Maximum length sequences (MLS) have been used to improve the signal-to-noise ratio (SNR) of otoacoustic emissions [Thornton, J. Acoust. Soc. Am. 94, 132-136 (1993)] and the auditory brainstem response [Thornton and Slaven, Br. J. Audiol. 27, 205-210 (1993)]. By implication, a shorter recording time would be required to give equal signal-to-noise ratio (SNR). This study aimed to establish whether it is also possible to improve the SNR of the auditory-evoked potential termed the middle latency response (MLR) using maximum length sequences (MLS). Recordings of 180 s each were made using a conventional recording rate and MLS rates of 42, 89, and 185 clicks/s. Three different stimulus intensities were used in the range 30 to 70 dB nHL. The rate of 89 clicks/s was found to produce most improvement in SNR for both the Na-Pa region of the MLR and the Na-Pb region. This improvement in SNR using MLS implies that an MLS rate of 89 clicks/s would produce a fourfold reduction in recording time for equal SNR over conventional recording for the Pa-Nb region of the MLR at a stimulus intensity of 70 dB nHL. The latency of the Nb wave was found to reduce significantly using MLS. An MLR could not be recorded from every subject in this study, but more subjects had an identifiable response for MLS than for conventional recordings. Use of MLS to record the MLR appears to offer the potential for reduction in test time and better wave identification.

Adult↗