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Biomedical subjects

L Stanton

Publications and source records attributed to L Stanton.

At least 19 recordsLinked to original sources
PubMed2004

Polygalacturonase-inhibiting proteins can function as activators of polygalacturonase.

The interaction between fungal endopolygalacturonases (EPGs) and polygalacturonase-inhibiting proteins (PGIPs) found in plant cell walls has been well established. The typical EPG/PGIP interaction is characterized by high affinity, reversibility, and a 1:1 stoichiometry that results in lowering the catalytic rate of a particular endopolygalacturonase by up to 99.7%. Various EPG and PGIP isoforms and glycoforms have been isolated and characterized, and combinations of EPGs and PGIPs demonstrate a range of enzyme inhibition. EPG/PGIP interactions have prompted many researchers to suspect the involvement of these proteins in the production of specific signals (oligosaccharins) during plant pathogenesis. We have recently reported on initial studies in our laboratory indicating that, for certain EPG/PGIP combinations, the specific activity of EPG is increased beyond that characteristic of the enzyme alone. In this paper, we present a detailed analysis of the product of the interaction of native Phaseolus vulgaris PGIP-2 with five EPGs from Aspergillus niger, namely PGI, PGII, PGA, PGB, and PGC in the presence of homogalacturonan. We demonstrate that for PGA and PGC, the interaction with PGIP-2 may result in either inhibition or activation in a manner that is pH dependent. This data suggests the need for a reevaluation of the conventional description applied to PGIPs; suggestions include polygalacturonase-binding protein and polygalacturonase-modulating protein.

Aspergillus niger↗
PubMed2002

Tuberculosis meningitis and attention deficit hyperactivity disorder in children.

The purpose of this study was to investigate the prevalence of attention deficit hyperactivity disorder (ADHD) in children who recovered from tuberculous meningitis (TBM) as part of an ongoing TBM research project. During this study, each TBM group subject underwent a thorough clinical-neurological examination, and a test battery which included the child behaviour check list (CBCL) Teacher's Report Form and Conners Rating Scale. The parents and teachers of each of the 21 TBM group and 21 control group subjects completed the above-mentioned questionnaires. All 21 TBM group subjects displayed symptoms of ADHD. The TBM group was significantly more hyperactive and unable to sustain attention than the control group. Furthermore, TBM group subjects were perceived as being significantly more unpopular, obsessive, compulsive and aggressive than the control group subjects. With regard to the frequency of externalizing behaviour, the TBM group subjects displayed significantly more externalizing behaviours as well as symptoms of attention deficit and hyperactivity. No significant differences between parents' and teachers' ratings were found. We conclude that ADHD is a common long-term complication of TBM.

Adolescent↗
PubMed1997

A peptide derived from neutrophil inhibitory factor (NIF) blocks neutrophil adherence to endothelial cells.

OBJECTIVE AND DESIGN: Peptides derived from neutrophil inhibitory factor (NIF), a known antagonist of Mac-1, were evaluated as inhibitors of neutrophil adherence. MATERIAL: In vitro assays of adherence employed: 1) human polymorphonuclear cells (PMN), 2) human umbilical vein endothelial cells (HUVEC), and 3) CHO cells expressing ICAM-1 (CHO-ICAM cells). TREATMENT: Cells, pretreated with NIF-derived peptides (0.1-100 microM) for 10 minutes, were permitted to adhere for 20 min in the continued presence of peptide. METHODS: Cell-based assays: 1) PMN adherence to HUVEC, 2) PMN adhesion to immobilized human serum proteins, and 3) adherence of CHO-ICAM cells to immobilized Mac-1. RESULTS: A NIF-derived peptide of 29 amino acids blocked PMN adherence to HUVEC, but behaved somewhat differently than the parent NIF protein. NIF specifically antagonized Mac-1 dependent adherence, but the peptide blocked neutrophil adherence that was dependent upon both Mac-1 and LFA-1 integrins. CHO-ICAM adherence to Mac-1 was blocked by NIF, but not by the peptide. Binding studies with NIF and the peptide indicate that the molecules bind to different sites. CONCLUSIONS: A peptide derived from NIF blocks PMN adherence but, unlike NIF, the mechanism of action is not mediated by direct antagonism Mac-1.

Amino Acid Sequence↗
PubMed1997

Urokinase thrombolysis as initial therapy for acute and non-acute ischemic extremities.

Limb ischemia, both acute and chronic, presents a risk to life and limb with mortality rates from 3% to 37% and amputation rates of the same range. Our experience with urokinase thrombolysis as the initial therapy for acute and non-acute ischemic extremities over 57 consecutive cases of native arterial occlusion by either thrombus or embolus has resulted in no mortality and only 3.5% requiring amputation (2 of 57). In 74% of cases initial thrombolytic therapy was followed by either balloon angioplasty (35 patients) or surgery (7 patients) to relieve the underlying cause of obstruction (i.e., stenosis, occlusion or aneurysm). Thrombolysis alone was sufficient and effective treatment in the remaining 26% (15 patients).

Adult↗
PubMed1996

The predictive value of biophysical profiles and Doppler velocimetry for fetal acidosis in a low risk population.

Antenatal fetal monitoring is the principal means of distinguishing the fetus requiring imminent delivery from that which is coping well in utero. The ability to detect fetal compromise, defined by fetal acidosis, in a low-risk population was evaluated in a prospective study of 50 women undergoing a Caesarean section in the absence of labour. The sensitivity and positive predictive value of a modified biophysical profile (BPP) or Doppler velocimetry to detect a fetus subsequently born with an umbilical artery pH of less than 7.20 was poor. The incidence of fetal acidosis in the population under study was 8%. Interpretation of antenatal fetal assessments must be tempered by the clinical features of each case. Decisions to deliver should take into account the low sensitivity of these tests in the absence of other complicating factors.

Acidosis↗
PubMed1989

Quality assurance breast phantoms for screen-film mammography: design and use.

Used properly, well-designed breast phantoms are a very useful part of the mammography QA program. However, they should be designed specifically for the purpose. The principles involved are discussed and illustrated by the design of the unit shown in figure 1. QA phantoms also must be applied appropriately. Procedures are described for checking the consistency of film density, evaluating image quality, and checking phototimer operation. The simple film density measurement test (table 2) also provides a useful check on the constancy of patient dose levels. However, errors may result when QA phantoms are used for dosimetry, primarily because their composition differs from that of the mixture BR12, which is usually taken as the standard for dosimetry measurement. Procedures are described for computing average glandular dose, as well as measuring the two required quantities: the beam HVL and the exposure in air required for proper film density.

Female↗
PubMed1987

Screen-film mammographic technique for breast cancer screening.

The values of dose and signal-to-noise ratio (SNR) for many techniques and breast thicknesses were computed and compared with a reference technique and breast thickness to provide a valid basis upon which to select a screening technique for screen-film mammography. The reference consisted of a Min-R/OM1 combination (or its equivalent) exposed through a 4.5-cm thick breast via 28 kV and a molybdenum target-beryllium window tube with a 0.03-mm Mo filter. Radiographs of an improved breast phantom were used to relate computed relative SNR values of techniques to diameters of the smallest calcific and soft-tissue objects demonstrated in mammograms. Without use of a grid, four Mo target/filtration combinations yielded similar computed dose and SNR levels, as did a tungsten target tube operated at 23 kV without a filter. Operation of the latter tube at 27.5 kV with a 0.051-mm rhodium filter should reduce dose by half but also SNR by 22%. However, such operation with a grid should greatly improve imaging moderate to large breasts without increasing dose over reference values.

Breast Neoplasms↗
PubMed1986

Human proto-oncogene N-myc encodes nuclear proteins that bind DNA.

N-myc is a gene whose amplification has been implicated in the genesis of several malignant human tumors. We have identified two proteins with molecular weights of 65,000 and 67,000 encoded by N-myc. The abundance of these proteins in tumor cells was consonant with the extent of amplification of N-myc. The two proteins apparently arose from the same mRNA, were phosphorylated, were exceptionally unstable, were located in the nucleus of cells, and bound to both single- and double-stranded DNA. These properties suggest that the products of N-myc and of the related proto-oncogene c-myc may have similar biochemical functions and that N-myc may be a regulatory gene. Our findings sustain the view that inordinate expression of N-myc may contribute to the genesis of several different human tumors.

Apudoma↗
PubMed1984

Dosage evaluation in mammography.

Estimates of breast dose per view are needed for selection of mammographic techniques and verification of their proper use. However, accurate dosimetry requires standardization of both the methodology and the assumed breast composition. Because several different methods have been reported, the authors developed a simple and reproducible method using a reference "average breast" composition of 50/50% water/fat by weight. Working curves were derived for average glandular and whole-breast dose per unit of exposure in air vs. HVL and thickness. When these curves are combined with on-site measurements of exposure per view, one obtains values of dose per view for each technique. Factors were also computed to correct dosage from the reference composition to other breast compositions.

Adult↗
PubMed1983

Breast radiography: phantom, equipment performance, and radiation dosage comparisons for twenty-eight major mammography centers in the midwest. Work in progress.

This preliminary report discusses mammography tests that were conducted at 28 midwest medical centers. Equipment-parameter measurements were made, and images that were obtained with the Stanton Mark IIR Mammography Phantom were studied to compare image quality. These tests indicate that variations in equipment parameters and techniques can result in differences in the imaging of various sized phantom fibril and speck groups.

Humans↗
PubMed1979

Auditory evoked potentials and auditory behavior following prenatal and perinatal asphyxia in rhesus monkeys.

Two types of asphyxia were studied in monkeys, total asphyxia during mid-pregnancy (94--98 days gestation) and combined partial and total axphyxia at term (165 days gestation). Auditory evoked potentials and the acquisition of 2 auditory discrimination tasks were studied in asphyxiated animals as well as in group of controls. The brains of all asphyxiates were examined histologically. No auditory discrimination deficit was found in the asphyxiated animals; however, the auditory evoked potentials differentiated between control and asphyxiated animals, especially those with verified inferior colliculus damage.

Animals↗
PubMed1979

Rapid computation of diagnostic X-ray bremsstrahlung spectra.

A method is described for rapid and accurate computation of diagnostic x-ray spectra. Accuracy limitations of Kramers' equation are overcome by providing intensity correction factors derived from published measured data. Use of a parameter based on the energy of the Kramers spectrum intensity peak permits deriving master factor curves which are remarkably independent of kVp, waveform and filtration. Computed and measured spectra generally agree to better than +/- 1 keV for beams generated at 100 kVp and below. Possible application of the method to higher energy diagnostic beams is discussed.

Mathematics↗
PubMed1979

A study of mammographic exposure and detail visibility using three systems: Xerox 125, Min-R, and Xonics XERG.

A breast phantom of novel design has been used to measure visibility of simulated calcific and soft-tissue fibrillar details in mammography, as well as to determine the roentgen exposure vs. depth. Exposure data were combined with a model of the breast as compressed during mammography to compute the mean exposure to the ductal parenchyma (MDE). Three different imaging systems were compared over a wide range of x-ray beam energies and breast characteristics. "Dosage" criteria other than the MDE are discussed.

Breast↗
PubMed1976

Clinical evaluation of electron radiography. Current status.

Details of a 4-phase evaluation of electron radiography are reported. The experimental equipment now uses liquid toners which result in less edge contrast and latitude than in powder-cloud exposures. Use of a bias technique during development prevents deposition except to areas where voltage exceeds the bias voltage. Quality radiographs with decreased doses and expense result.

Electrons↗