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Biomedical subjects

G Michael

Publications and source records attributed to G Michael.

At least 19 recordsLinked to original sources
PubMed2005

A method for benchmarking CT scanners.

This study involved the development of an objective method to compare the performance of five CT scanners for the purpose of benchmarking. The method used to assess the scanners was to determine the dose-normalised noise at a spatial resolution of 5.5 cm(-1). This gave a dose-normalised percent noise between 0.37% and 0.76%. The scanners were also assessed for radiation dose to patients undergoing abdomen and head CT examinations. Patients' dose-length product (DLP) for the abdomen clinical examinations varied from 305 to 685 mGy-cm, and for the head clinical examinations from 333 to 900 mGy-cm. The study results demonstrated that the comparison of dose and spatial resolution normalised percent noise levels is a useful method of comparing CT scanner performance.

Australia↗
PubMed2002

Attenuation of diagnostic energy photons by polymer gel dosimeters.

Post-irradiation changes in the linear attenuation coefficient, mu, of polymer gel dosimeters give rise to a change which can be measured with x-ray computed tomography. Polymer gel dosimeters were manufactured consisting of 3% (by weight) acrylamide and 3% N,N'-methylene-bis-acrylamide comonomers dissolved in aqueous gelatin (5% gelatin by total weight and 89% de-ionized distilled water). Mu was measured in a collimated radiation beam of photons from an 241Am source. Density, rho, of polymer gel dosimeters was measured using volumetric flasks with capillary stoppers. The measured post-irradiation data of mu was plotted against the data of rho for different batches, and linear least squares fits gave r2 values of 0.99605 and 0.99953, with P values of less than 0.001. This confirms that the post-irradiation change in mu is proportional to that of rho. The change in rho implies a change in volume regardless of the evaluation modality of the polymer gel dosimeter.

Dose-Response Relationship, Radiation↗
PubMed2001

An experimental study of the dose response of polymer gel dosimeters imaged with x-ray computed tomography.

Changes in the linear attenuation coefficient of polymer gel dosimeters post-irradiation enable the imaging of dose distributions by x-ray computed tomography (CT). Various compositions of polymer gel dosimeters manufactured from acrylamide (AA), and N,N'-methylene-bis-acrylamide (BIS) comonomers and gelatin or agarose gelling agents were investigated. This work shows that increasing the comonomer concentration increases the CT-dose sensitivity of the polymer gel dosimeter. This can be further increased by replacing gelatin with agarose. Varying the gelatin concentration however does not significantly change the CT-dose sensitivity. Among the compositions studied, dose resolution (D(delta)95%) was found to be optimal for polymer gel dosimeters comprising 5% gelatin, 3% AA, 3% BIS and 89% water.

Acrylamide↗
PubMed1999

Reference values of facial features in Scandinavian children measured with a range-camera technique.

Reference values of facial features in white Scandinavian children were ascertained using a newly developed range-camera technique with a three-dimensional measuring program specifically designed for anthropometric measurements. Seven facial features in 613 healthy subjects (322 girls, 291 boys), aged 1 month to 18 years, and nine subjects with the fetal alcohol syndrome,aged 7 to 18 years, were studied. Data were analysed by multivariate multiple regression and measurements of each facial feature plotted against age and presented as curves, with 95% and 99% univariate prediction limits. All children with fetal alcohol syndrome had shorter palpebral fissures, and in six of them the outer canthal distance was shorter than that in the reference group. The reference values presented may be useful in clinical practice--for example, in the evaluation of children with syndromes that result in dysmorphology of the face and in the planning of plastic and reconstructive surgery.

Adolescent↗
PubMed1998

[Use of G-CSF (Neupogen) in multimodal treatment in radiotherapy].

BACKGROUND: Therapy-induced leukopenias with corresponding consequences repeatedly occur in radiotherapy using combined modalities treatment. In radiotherapy, where G-CSF (granulocyte-colony-stimulating-factor) is not licensed, G-CSF has been used successfully under individual circumstances. These results were confirmed in several studies with small patient groups. The aim of this study was to check former results in a larger patient group, to verify postulated side effects and specially to define a cost-effective schedule in the treatment with G-CSF (Neupogen). PATIENTS AND METHODS: In this surveillance trial 50, partially previously treated patients with different malignant tumors were treated with G-CSF. According to the probability of a leucocytosis lower than 1000/mm3, G-CSF (Neuropogen) was already given at leukocyte values lower than 2500/mm3 (500/mm3 bis 2450/mm3). It administered subcutaneously every other day, based on body weight until reaching normal leucocyte levels. RESULTS: In 92% of the patients the increase of leucocytes occurred in the first 24 hours. On average G-CSF was given 4.9 times per patient. Patients without prior therapies or less complex therapies needed less G-CSF applications (3.5 to 5.8 applications). Due to individually varying leucocyte courses the G-CSF therapy was started with leucocyte values between 500/mm3 and 2450/mm3. Patients who were treated with up to 3 G-CSF applications had higher leucocyte levels than those with 4 or more applications (1620/mm3 to 1250/mm3). Leucopenia related infections, therapy interruptions or break-offs did not occur. Besides light "flu like" symptoms in 14% of the patients, no side effects were observed. CONCLUSIONS: When a decrease of leucocyte values lower than 1000/mm3 is expected, the most cost-effective treatment is given when starting the interventional G-CSF administration already at leucocyte values around 1600/mm3. Leucopenias can be treated effectively, with little side effects and in a cost-effective way when G-CSF is given on time.

Adult↗
PubMed1998

Assessment of facial features with a range camera.

We describe a new method for the quantitative analysis of facial features using a range camera with a three-dimensional measuring program. The range camera consists of a video camera, a light projector, and a computer. The video camera captures a number of images of different light patterns projected on to the face. From these, a "range image" is computed. One fully illuminated intensity image of the face is also taken. By defining anatomical landmarks manually on the intensity image, three-dimensional measurements are automatically obtained from corresponding positions in the range image. The method is highly accurate and precise, and is a simple and reliable way of assessing facial features. We recommend that the system be adapted in clinical practice--for example, in diagnosing syndromes and planning plastic and reconstructive surgery.

Cephalometry↗
PubMed1995

Molecular cloning of a new member of the p21-Cdc42/Rac-activated kinase (PAK) family.

A number of "target" proteins for the Rho family of small GTP-binding proteins have now been identified, including the protein kinases ACK and p65PAK (Manser, E., Leung, T., Salihuddin, H., Zhao, Z.-S., and Lim, L. (1994) Nature 367, 40-46). The purified serine/threonine kinase p65PAK has been shown to be directly activated by GTP-Rac1 or GTP-Cdc42. Here we report the cDNA sequence encoding a new brain-enriched PAK isoform beta-PAK, which shares 79% amino acid identity with the previously described alpha-isoform. Their mRNAs are differentially expressed in the brain, with alpha-PAK mRNA being particularly abundant in motor-associated regions. In vitro translation products of the alpha- and beta-PAK cDNAs exhibited relative molecular masses of 68,000 and 65,000, respectively, by SDS-polyacrylamide analysis. A specific beta-PAK peptide sequence was obtained from rat brain-purified p65PAK. Recombinant alpha- and beta-PAKs exhibited an increase in kinase activity mediated by GTP-p21 induced autophosphorylation. Cdc42 was a more potent activator in vitro of alpha-PAK kinase, and the fully activated enzyme is 300 times more active than the unphosphorylated form. Interestingly the down-regulation in the binding of p21s to recombinant beta-PAK and brain p65PAK, which is observed upon kinase activation does not occur with recombinant alpha-PAK.

Amino Acid Sequence↗
PubMed1993

Clinical implications of HIV seroprevalence in childbearing women: the Louisiana experience.

An epidemiologic analysis of the HIV Seroprevalence Survey of Childbearing Women in Louisiana and the Louisiana AIDS Surveillance Report was conducted to inform health care practitioners of the trends in HIV infection and AIDS cases in women and children. HIV seropositivity in childbearing women has increased by 64% from 1988 to 1991 with an overall rate of 0.15% (202,178 tested). The rate in Orleans Parish is 0.53% (22,833 tested). Louisiana pediatric AIDS cases have increased yearly with 85% due to perinatal transmission. Assuming a 30% perinatal transmission rate, approximately 93 children are expected to develop AIDS in Louisiana within the next few years. Because of anticipated larger numbers of pediatric AIDS cases, health care providers for women and children need to identify their HIV infected patients so that early intervention can begin.

Acquired Immunodeficiency Syndrome↗
PubMed1990

[The results of radiotherapy of epicondylitis humeri using different dosages].

In a prospective analysis the effectiveness of roentgen irradiation with minimal doses (daily single doses .03 Gy up to a total dose of 1.5 Gy) was investigated in 207 patients with an epicondylitis humeri. Compared with a group of 92 patients, who were irradiated with higher doses being in general use (weekly 2x single doses 1.0 Gy to a total dose of 4.0 Gy), the therapeutic results show no significant differences. After termination of the first irradiation series an improvement of complaints was seen in half of the patients (48.8% or 50.0%). A further increase of the quota in success to 74.9% or 70.6% was found 6 weeks after termination of irradiation. By reason of radiotherapeutic results, mainly attained in chronic states of epicondylitis humeri after primary conservative therapy without success for months and partly surgical pretreatment, the radiotherapy should be used more frequently than till now, especially in consideration of its slight side-effects and injuries of patients.

Adult↗
PubMed1985

Novel opioid peptide amidorphin: characterization and distribution of amidorphin-like immunoreactivity in bovine, ovine, and porcine brain, pituitary, and adrenal medulla.

We have recently isolated from bovine adrenal medulla a novel C-terminally amidated opioid peptide, amidorphin, which derives from proenkephalin A. Amidorphin revealed a widespread distribution in bovine, ovine, and porcine tissue. Particularly high concentrations of amidorphin immunoreactivity were detected in adrenal medulla, posterior pituitary, and striatum, similar to the major gene products of proenkephalin A. In the adrenal medulla of each species, authentic amidorphin was the predominant immunoreactive form. Pituitary and brain, however, contained predominantly putative N-terminally shortened fragments of amidorphin of a slightly lower molecular weight and shorter retention times on HPLC. In addition, in ovine adrenal medulla, a putative high-molecular-weight form of amidorphin was detected. These findings are indicative of a tissue-specific processing of the proenkephalin A precursor, leading predominantly to authentic amidorphin in the adrenal medulla and further processing to smaller C-terminal fragments in the brain and pituitary.

Adrenal Medulla↗
PubMed1984

Quality of care in managing hypertension by case finding in north west London.

The records of patients who were registered with general practice in inner London and outer London (both training and non-training practices) were examined for details of blood pressure recordings. A blood pressure recording was found in the past five years in only 22% of the notes of inner London practices but in 43% of notes in outer London practices, there being no difference between training and non-training practices. In 31% of the notes with a blood pressure recording the blood pressure had been raised (greater than or equal to 160/90) at some time: in 62% of these notes for patients aged 65 or more and in 52% of these notes for patients aged under 65 treatment had been given at some time. Thirty eight per cent of patients in the older group and 33% in the younger group were being treated at the time of the survey, thiazides being the most commonly used drugs. Thirty four per cent of all those with a raised blood pressure at some time had a latest recording of under 90 mm Hg diastolic. There seems to be a continuing need for general practitioners to detect and treat hypertension, and it is suggested that general practitioners should consider using systematic case finding for hypertension in their practices.

Adult↗
PubMed1984

Shared determinants of native and denatured bovine serum albumin are recognized by both B- and T-cells.

The antigenic relationship between native and denatured bovine serum albumin (BSA) was investigated by examining specificity of antibodies directed against both proteins. Polyclonal antibodies produced to native and denatured BSA in hyperimmunized mice were specific for the homologous molecule. In contrast, polyclonal antibodies formed early in the response to native BSA reacted both the denatured and the native molecule. Monoclonal antibodies to native BSA were specific for the homologous antigen, while one of three clones prepared by immunization with denatured BSA produced an antibody cross-reactive with native BSA. Our results suggest that shared determinants of native and denatured BSA molecules can be recognized by both B- and T-cells.

Animals↗
PubMed1982

Antibody production and antigenic specific suppression to bovine serum albumin in uremic rats.

Antibody response and antigen specific suppression to bovine serum albumin (BSA) in uremic rats have been investigated. Primary immune response was found to be significantly reduced independent of the route of administration or adjuvant while secondary response was affected only in animals in which a weak adjuvant such as Al(OH)3 was used. Antigen specific suppression of uremic rats was achieved by intravenous pretreatment with BSA or a C terminal fragment (505-582) of BSA. Secondary response in sham operated controls was suppressed by BSA but not by the fragment. There was about five-fold greater retention of the fragments in the uremic rats than in sham-operated controls at a 6 hr or later after i.v. administration.

Animals↗