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Biomedical subjects

F W Smith

Publications and source records attributed to F W Smith.

At least 145 records · Page 8Linked to original sources
PubMed1985

The nuclear magnetic resonance appearances of neuroblastoma.

In addition to being a non-ionising method of imaging, nuclear magnetic resonance has the ability to demonstrate the body organ using different radio pulse sequences in order to highlight different tissues. Neuroblastomas are best demonstrated using proton spin lattice relaxation time (T1) weighted images such as inversion recovery or calculated T1, rather than proton density. The ability to produce sections in the sagittal and coronal as well as the axial plane allows for accurate tumour localisation and management planning. The appearances of primary neuroblastoma and metastatic spread to bone are described in three cases of neuroblastoma.

Adolescent↗
PubMed1985

Particulate oral NMR contrast agents.

Insoluble paramagnetic compounds in suspension can be used to achieve visualization of the gastrointestinal system on magnetic resonance imaging (NMR). Particulate preparations of these agents decrease the T1 and T2 of solutions to which they are added. Gadolinium oxalate, a prototype of these particulate agents, was evaluated in vitro and in vivo (in rabbits) by NMR imaging. The effect of this compound upon T1 and T2 in vitro was also quantitated by NMR spectroscopy. Opacification of the upper gastrointestinal tract was achieved with gadolinium oxalate following oral administration. The colon was visualized following rectal administration.

Administration, Oral↗
PubMed1985

Mascara--an unsuspected cause of magnetic resonance imaging artifact.

It is well recognised that metals, especially iron, will cause artifacts in magnetic resonance (MR) images. Hitherto it has not been recognised that some facial cosmetics contain magnetic materials, in sufficient quantities to cause artifacts. We report a case of a 25-year-old female who had MR images of her orbits made while wearing mascara eye makeup. The resultant images showed distortion of the signal over the anterior aspect of both eyes. Examination following the removal of the eye makeup resulted in the acquisition of normal images. The typical ingredients of mascara are natural and synthetic waxes, glycerine, water, kaolin, preservatives, polymer film formers and pigments. A wide range of pigments may be used, especially iron oxide, which is a constituent of both brown and blue mascara. In addition it is likely that a number of mascaras will be contaminated with heavy metals. As a result of this observation we now ensure that all patients who are undergoing MR imaging of the head, remove all facial cosmetics as well as any jewelry prior to imaging.

Adult↗
PubMed1985

Nuclear magnetic resonance in adrenoleukodystrophy: report of a case.

The nuclear magnetic resonance images obtained in a case of adrenoleukodystrophy are presented. The areas of demyelination are clearly seen. The T1 values of the affected areas are not specific and coincide with those previously recorded in the lesions of multiple sclerosis or cerebrovascular disease. A diagnosis of adrenoleukodystrophy should be considered in younger male patients presenting with behavioural disturbances, especially when these are associated with abnormalities of vision or gait. There may be no clinical evidence of the associated adrenocortical insufficiency.

Adrenal Glands↗
PubMed1985

Short (35-cm) versus long (60-cm) flexible sigmoidoscopy: a comparison of findings and tolerance in asymptomatic patients screened for colorectal neoplasia.

The purpose of this study was to compare the utility of the 35-cm versus the 60-cm flexible sigmoidoscope in screening asymptomatic patients for colorectal neoplasia. Two hundred fifty-eight patients 45 years of age or older were examined in a randomized fashion with both the 35-cm and 60-cm instruments. Fifteen percent (39/258) of patients had a total of 50 polypoid lesions 3 mm or greater in diameter (including one carcinoma). Of all polypoid lesions, 76% were detected with the 35-cm instrument compared to 98% with the 60-cm sigmoidoscope. Eighty-four percent of all polyps occurred within the distal 35 cm of colon. The mean time required to complete the examination was significantly less with the 35-cm sigmoidoscope than with the 60-cm sigmoidoscope (2.5 vs. 5.7 min). Moderate to severe discomfort was experienced by 69% of patients with the 60-cm instrument compared to only 29% with the 35-cm sigmoidoscope. Seventy-two percent of patients preferred examination with the shorter instrument compared with 7% for the longer sigmoidoscope, while 21% of patients expressed no preference. The 35-cm flexible sigmoidoscope fulfills many criteria of an effective screening test for colorectal neoplasia including rapidity of examination, safety, good sensitivity, and excellent patient acceptance.

Aged↗
PubMed1985

Nuclear magnetic resonance imaging--a new look at the fetus.

A new form of obstetric imaging using nuclear magnetic resonance (NMR) has been assessed for use in pregnancy. A total of 92 examinations were performed in 62 women during the second and third trimesters in both normal and complicated pregnancies including 14 with diabetes, six with pre-eclampsia and four with intrauterine growth retardation. Our experience has shown that NMR imaging gives excellent differentiation of both maternal and fetal tissues, and because of complete penetration both superficial and deep structures have been clearly identified. The best fetal images were obtained most consistently in the third trimester providing good detail of brain, lungs, liver, heart, bladder, subcutaneous fat, placenta and umbilical cord while maternal tissues were clearly seen at all gestations. As this form of imaging uses no ionizing radiation it offers an alternative means with unique capabilities for investigating pregnancy.

Biometry↗
PubMed1985

Nuclear magnetic resonance (NMR). II. Imaging in dementia.

Proton NMR imaging of the brain is rapidly becoming established as a useful investigative tool in medicine. This paper examines the usefulness of the NMR parameters--spin-lattice relaxation time (T1) and proton density (PD)--in differentiating groups of patients with senile dementia of Alzheimer type (SDAT) and multi-infarct dementia (MID) from each other, and from elderly controls. T1 values increase with severity of dementia. NMR parameters may also be of use in localising regions of brain damage.

Aged↗
PubMed1985

The relationship between Parkinson's disease and dementia. A study using proton NMR imaging parameters.

The value of the spin lattice relaxation time (T1) obtained during nuclear magnetic resonance imaging of the brain was studied in patients with idiopathic Parkinson's disease, with and without dementia. T1 increases significantly in the basal ganglia and cerebral white matter of the demented and non-demented groups. T1 of the cerebral white matter correlates with the severity of dementia.

Aged↗
PubMed1985

Nuclear magnetic resonance tomography of the orbit at 3.4 MHz.

The significantly different signals from the various structures within the orbit suggest that NMR tomography will prove to be a valuable method for the diagnosis of both ocular and orbital disease. The resolution of the technique is initially illustrated by the demonstration of the signal patterns from the normal globe and orbit. The characteristic features of some pathological conditions, including vitreous haemorrhage and retinal detachment, are then shown. The value and limitations of the technique in differentiating conditions such as choroidal haemorrhage from malignant melanoma, and intra-orbital lymphoma from pseudo-tumour, are illustrated and discussed. The absence of artefact from bone, synthetic lens implants and non-ferromagnetic metallic foreign bodies is stressed.

Clinical Trials as Topic↗
PubMed1985

The potential use of nuclear magnetic resonance imaging in pregnancy.

Nuclear magnetic resonance (NMR) imaging is a new technique for in-vivo human imaging. The technique does not use ionizing radiation but employs a radiofrequency pulse and a strong magnetic field to map the hydrogen proton distribution in the body. Since most of the hydrogen in the body is present in either water or fat it is the best imaging method yet devised for displaying the soft tissues of the body. The principles of NMR imaging are briefly described in simple terms for the benefit of the reader not yet familiar with the technique before discussing its potential use in the study of the developing fetus. The absence of ionizing radiation together with the good resolution soft tissue images allow for accurate demonstration of the uterus, placenta and fetus in the pregnant patient. Prior to 22 weeks gestation the fetus may be difficult to image due to its movement during imaging. After 26 weeks the fetus is generally well demonstrated and measurements of fetal size easily made. Observations of the fetal brain, lungs, heart, liver and genito-urinary tract are possible and by measuring the strength of the NMR signal the development of these fetal organs may be made. In the fetus of the diabetic mother measurement of the fetal subcutaneous fat is possible and may be of use in assessing gestational age. The placenta is easily localized even when situated posteriorly. Observations of maternal organs are also possible, especially the kidneys and spine.

Embryonic and Fetal Development↗
PubMed1985

The value of Tc-DTPA transit times and NMR T1 measurements in monitoring the progress of renal transplants.

The value of 99Tcm-DPTA transit times and NMR T1 measurements in monitoring the progress of renal transplants has been investigated. Renal transit times were calculated from 182 renograms performed on 29 patients and from 22 of these patients 67 proton spin-lattice relaxation time (T1) measurements were obtained using the Aberdeen Mk 2 NMR Imager. The clinical status of each patient at the time of investigation was defined in retrospect. The principal value of the mean transit time (MTT) was in differentiating between acute rejection and other causes of raised plasma creatinine. During a rejection episode the MTT is raised out of the normal range of 227 +/- 26 s but with chronic rejection or other causes of raised plasma creatinine the MTT remains within normal limits. NMR T1 values appeared to be of little diagnostic value as the normal range was found to be very wide ranging from 340 to 640 ms.

Creatinine↗
PubMed1984

Purification of Escherichia coli DNA photolyase.

Escherichia coli photolyase is a DNA repair enzyme which monomerizes pyrimidine dimers, the major UV photoproducts in DNA, to pyrimidines in a light-dependent reaction. We recently described the construction of a tac-phr plasmid that greatly overproduces the enzyme (Sancar, G. B., Smith, F. W., and Sancar, A. (1983) Nucleic Acids Res. 11, 6667-6678). Using a strain carrying the overproducing plasmid as the starting material, we have developed a purification procedure that yields several milligrams of apparently homogeneous enzyme. The purified protein is a single polypeptide that has an apparent Mr of 49,000 under both denaturing and nondenaturing conditions. The enzyme has no requirement for divalent cations and it restores the biological activity of irradiated DNA only in the presence of photoreactivating light. The purified photolyase has a turnover number of 2.4 dimers/molecule/min; this value agrees well with the in vivo rate of photoreactivation in E. coli.

DNA Repair↗
PubMed1984

Sequences of the Escherichia coli photolyase gene and protein.

We have determined the nucleotide sequence of a 2039-base pair segment of Escherichia coli chromosomal DNA containing the phr gene, which encodes deoxyribopyrimidine photolyase. The coding region of phr is 1416 base pairs and is preceded by regions homologous to consensus sequences for E. coli promoters and ribosome binding sites. The phr gene is preceeded by an open reading frame of 169 codons (orf169) which is transcribed in the same direction. The proximity of orf169 to phr suggests that both are members of a single operon containing one or more internal promoters allowing differential expression of phr. An unusually large number of rare or infrequently used codons are utilized in phr, which may contribute to the low copy number of photolyase. The sequence at the NH2 and COOH termini and the overall amino acid composition of mature photolyase, determined using purified protein, agrees with predictions based upon the nucleotide sequence. Photolyase consists of 471 amino acids and has a calculated molecular weight of 53,994.

Amino Acid Sequence↗