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Biomedical subjects

A R Smith

Publications and source records attributed to A R Smith.

At least 19 recordsLinked to original sources
PubMed1992

Transformation of synthetic pyrethroid insecticides by a thermophilic Bacillus sp.

Employing a mineral salts medium containing Tween 80 as the primary carbon source, a strain of Bacillus stearothermophilus was isolated which was able to hydrolyse selected second and third-generation pyrethroids to non-insecticidal products. Of a range of pyrethroid insecticides the trans-isomer of permethrin was the most readily transformed by this microbial isolate, whilst flumethrin was the least. 3-Phenoxybenzoic acid and the respective halovinyl or haloacid moieties were detected as the major hydrolytic products of the pyrethroids. It is believed that 3-phenoxybenzoic acid was formed from 3-phenoxybenzyl alcohol which was not however detected as an intermediate in these systems. 3-Phenoxybenzoic acid was further transformed to 4-hydroxy-3-phenoxybenzoic acid. A potential metabolic pathway has been described.

Benzoates↗
PubMed1992

Improved methods for determination of variability in patient positioning for radiation therapy using simulation and serial portal film measurements.

Variability in patient positioning was determined by analyzing simulation and portal film measurements for 318 portals in 51 patients treated with external beam radiotherapy to the head and neck. Several indicators of error in patient positioning were examined: random error, a measure of the deviation of all portal films from the average portal film position, systematic error, a measure of the difference between the average portal film and the simulation film, and total uncertainty, a measure of the overall deviation, including both random and systematic uncertainties. The median differences noted were 0.4 cm, 0.6 cm, and 0.7 cm, for Random Error, Systematic Error, and Total Uncertainty, respectively. The treatment fields analyzed in this study show a substantial treatment-to-treatment and simulation-to-treatment variability in patient positioning. The methods described provide an improved means for the systematic analysis of variability in patient positioning.

Head and Neck Neoplasms↗
PubMed1992

Evaluation of multileaf collimator design for a photon beam.

Various aspects of multileaf collimator (MLC) design are examined relative to clinical requirements. The characteristics studied included: (a) irregular field edge definition or "effective" penumbra, (b) optimum field coverage for the multileaf portion of the field, and (c) leaf velocity. A film dosimetry technique was developed to measure the rapid 2-dimensional change in dose at an edge defined by a multileaf collimator with the segments staggered. The method applies a correction factor which allows for the changing ratio of scattered to primary photons at the field edge so that the energy dependence of the film is corrected. Stepped lead alloy blocks were irradiated with 6 MV photons to obtain films simulating a double-focused multileaf collimator, and the results were compared to films of fields shaped with standard divergent blocks. The effect of the shape of the leaf face (the end of the leaf) on penumbra was also studied. Proper shaping of the leaf ends may eliminate the need to exactly match beam divergence so that the mechanical of the collimator system is simplified. Leaves having several different end shapes and moving horizontally to intercept a vertical beam were compared to the divergent design where a straight face moves along an arc. The measurements showed that the "effective" penumbra (measured as the distance from the 80 to 20% isodose lines) for the multileaf collimator is a function of the angle between the direction of leaf motion and the edge defined by the leaves. In addition, all leaf end shapes showed some increase in penumbra compared to standard divergent blocking and also had increasing penumbra width as they moved over or back from the field center line. A total of 459 treatment fields and six disease sites were examined to determine the percentage of fields potentially shaped by multileaf segments of specified length. This study showed 93% of the fields had lengths of 30 cm or less and 99% had widths of 25 cm or less. A study conducted to determine the required leaf velocity to shape various target volume configurations during complete rotation (at 1 RPM) showed that a leaf speed of at least 1.5 cm/sec at isocenter is needed for dynamic conformal treatment.

Equipment Design↗
PubMed1992

Factors affecting antibacterial activity of hop compounds and their derivatives.

The antibacterial effect of weak acids derived from the hop plant (Humulus lupulus L.) increased with decreasing pH. Analysis of the minimum inhibitory concentration of such compounds against Lactobacillus brevis IFO 3960 over pH 4-7 suggests that undissociated molecules were mainly responsible for inhibition of bacterial growth. The antibacterial activity of trans-isohumulone was ca 20 times greater than that of humulone, 11 times greater than that of colupulone and nine times greater than that of trans-humulinic acid when the degree of ionization was taken into account. Monovalent cations (K+, Na+, NH4+, Rb+, Li+) stimulated antibacterial activity of trans-isohumulone but the effect was smaller than that observed with H+. The response to divalent cations varied: Ca2+ had little effect on antibacterial activity, whereas Mg2+ reduced activity. Lipid materials and beta-cyclodextrin also antagonized the antibacterial action of trans-isohumulone.

Anti-Bacterial Agents↗
PubMed1992

Effect of hysterectomy on anorectal and urethrovesical physiology.

To investigate whether vaginal or total abdominal hysterectomy is associated with changes in anorectal and urethrovesical physiology, 26 women were studied before operation and six weeks and six months afterwards. The results showed a postoperative increase in both rectal and vesical sensitivity (p less than 0.01). Similar results were observed irrespective of the type of hysterectomy. No significant changes in rectal or bladder compliance were noted, and anal pressure and urethral pressure and length were unchanged after surgery. Whole gut transit was not affected by hysterectomy. Urinary symptoms occurred de novo in 6/26 women and gastrointestinal symptoms in 2/26 women. These results show that significant changes in rectal and vesical sensitivity occur after hysterectomy for benign disease. These persist for at least six months postoperatively but are not always associated with development of urinary or gastrointestinal symptoms.

Adult↗
PubMed1992

Relation between hysterectomy and the irritable bowel: a prospective study.

Some women with irritable bowel syndrome date the onset of symptoms to previous hysterectomy. To assess prospectively the incidence of gastrointestinal symptomatology arising de novo after hysterectomy, and to study the effect of surgery on pre-existing symptoms, 205 women completed a symptom questionnaire before and six weeks and six months after surgery. Beforehand, symptoms suggestive of irritable bowel syndrome occurred in 22% of patients. At six months after operation, 60% of these had improved or were symptom free while 20% had increased symptomatology. New gastrointestinal symptoms were present more than once per week in 10% of previously asymptomatic women. Constipation predominant irritable bowel syndrome was the commonest symptom complex seen de novo, occurring more than once per week in 5% of the group. No relation was found between new symptomatology and the type of hysterectomy, oophorectomy, or the administration of perioperative antibiotics. This study suggests that many women with pre-existing gastrointestinal symptomatology improve after hysterectomy. However, symptoms suggestive of irritable bowel syndrome do arise de novo in 10%. As hysterectomy is common, gastroenterologists can expect to see women presenting with post-hysterectomy problems.

Adult↗
PubMed1992

Evaluation of an enzyme-linked immunosorbent assay for detection of Eperythrozoon suis antibodies in swine.

An ELISA was developed and tested to detect antibodies to Eperythrozoon suis in swine. Results were compared with those of the indirect hemagglutination (IHA) test. Antigen isolated from swine heavily infected with E suis was used for both tests. Comparison of the ELISA with the IHA test revealed a significant (P less than 0.001) correlation between results. Of 114 samples obtained from 9 swine infected with E suis, 87.7% were seropositive (titer greater than or equal to 200) via the ELISA, and 80.7% were seropositive (titer greater than or equal to 20) via the IHA test. The sensitivity of the ELISA was greater than that of the IHA test. All blood samples obtained from specific-pathogen-free swine tested negative for E suis antibody. Cross-reactions were not observed between E suis antigen and antisera against various swine and cattle disease agents using ELISA. We concluded that the ELISA may be used for rapid and effective diagnosis of infection with E suis in swine.

Animals↗
PubMed1992

Squamous carcinoma.

Explore the source record for details and available documents.

Carcinoma, Squamous Cell↗
PubMed1992

Ticlopidine: a new platelet aggregation inhibitor.

The chemistry, pharmacology, pharmacokinetics, clinical efficacy, adverse effects, and dosage of ticlopidine are reviewed. Ticlopidine appears to inhibit platelet aggregation induced by adenosine diphosphate. Ticlopidine hydrochloride is rapidly absorbed after oral administration, and maximum antiplatelet effects occur one to three hours after the dose. In multicenter, randomized, double-blind trials, ticlopidine was more effective than aspirin or placebo in preventing stroke, myocardial infarction, or death caused by vascular events. Ticlopidine was more effective than aspirin in preventing recurrent transient ischemic attacks after six months of therapy. Ticlopidine has also been used to prevent occlusion and improve patency of aortocoronary bypass grafts, to prevent ischemic ulcers in patients with chronic arterial occlusive disease, and to slow the progression of diabetic microangiopathy. The most serious adverse effect, neutropenia, occurred in about 1% of patients. The most frequently reported adverse effects are diarrhea, nausea, vomiting, and abdominal cramps. Ticlopidine is indicated for reducing the risk of thrombotic stroke in patients who have experienced a minor stroke, transient ischemic attack, or completed thrombotic stroke. The recommended dosage is 500 mg/day in two divided doses taken with food. Ticlopidine is an alternative agent for the primary and secondary prevention of stroke. Because of the risk of neutropenia and agranulocytosis and the high cost of therapy, ticlopidine should be reserved for patients who are intolerant of or lack benefit from aspirin.

Animals↗
PubMed1991

The normal growth patterns of New Zealand preschool children.

This study was designed to update New Zealand Growth Charts for preschool children. The heights, weights and head circumferences of 12,311 children aged one month to five years were recorded. From this data growth charts were constructed. Since significant differences were found between the measurements for boys and girls, separate graphs were constructed. We strongly advise that these graphs be used by all health professionals involved with child health surveillance of the 0-5 age group.

Body Height↗
PubMed1991

Screening for lupus anticoagulant and anticardiolipin antibodies in women with fetal loss.

Sixty six women with first or second trimester fetal loss were investigated for the presence of lupus anticoagulant by routine coagulation tests and the dilute Russell's viper venom time with a platelet neutralisation procedure, and for raised anticardiolipin antibodies by an enzyme linked immunosorbent assay. Of 35 women with recurrent fetal loss, seven were positive for lupus anticoagulant and six had increased IgG anticardiolipin antibodies, while of 31 women with only one or two episodes of fetal loss, one had lupus anticoagulant and none increased IgG anticardiolipin antibodies. These findings were significantly different. There was no difference in the incidence of increased IgM anticardiolipin antibodies between the two groups (three and two cases, respectively). A further 11 women with intrauterine death in the third trimester were studied and lupus anticoagulant and raised IgM anticardiolipin antibodies were found in one case. No woman was known to have systemic lupus erythematosus. It is concluded that lupus anticoagulant and increased IgG anticardiolipin antibodies are independently associated with recurrent first and second trimester fetal loss and that such cases should be investigated, even in the presence of otherwise good health, by a comprehensive methodological approach.

Abortion, Habitual↗
PubMed1990

An Eperythrozoon-like parasite in llamas.

An Eperythrozoon-like RBC parasite was found in a herd of llamas in western Kentucky. The light microscopic and electron microscopic features of the organism were similar to those of E suis. Results of an indirect hemagglutination test for E suis were positive with sera from some parasitemic and nonparasitemic llamas. Parasitemic llamas were usually less than 1 year old and had more severe clinical signs of disease than did older llamas. Poor weight gain and growth, anorexia, and prolonged recumbency were the principal signs of disease. Anemia was usually mild and not accompanied by icterus. Hypoglycemia was associated with parasitemia. Some response to oral or parenteral treatment with tetracycline was noticed, but recrudescence of the infection in some treated llamas was observed. Llamas in nearly every region of the United States have had titers in approximately 12% of samples tested, suggesting that infection with the organism may be widespread. Parasitemic llamas have been recognized in at least 8 states.

Animals↗
PubMed1990

A geochemical assessment of terrestrial gamma-ray absorbed dose rates.

A survey of the geochemical literature and unpublished data has resulted in the classification of the concentrations of the naturally occurring radioelements U, Th, and K by their associated rock types. A data base of over 2500 entries has been compiled, permitting calculation of terrestrial gamma-ray absorbed dose rates. The general lithology of terrains may be distinguished by their radioelement ratios, relative abundances, and total gamma radioactivities. The gamma-ray absorbed dose rates in air above igneous rocks generally vary with their silica contents, and with the exception of shale, sedimentary rocks have lower K:U and K:Th ratios than most igneous rocks. The appreciable difference between the overall mean terrestrial gamma-ray dose rate for rock of the continental surface (approximately 7 X 10(-8) Gy h-1) and the mean dose rate from field measurements over soil (approximately 5 X 10(-8) Gy h-1) is explained by the substantial differences between radioelement concentrations of soil and rock, differences that may vary markedly with rock type.

Gamma Rays↗
PubMed1990

Identification of a new membrane-associated polypeptide specified by the coronavirus infectious bronchitis virus.

Nucleotide sequences from the third open reading frame of mRNA D (D3) of infectious bronchitis virus (IBV) were expressed in bacteria as part of a fusion protein with beta-galactosidase. Antiserum raised in rabbits against this fusion protein immunoprecipitated from IBV-infected chick kidney or Vero cells a polypeptide of 12.4K, the size expected for a D3-encoded product. The D3 polypeptide is apparently non-glycosylated, and appears to be associated with the membrane fraction of infected cells, as judged by cell fractionation and immunofluorescence.

Amino Acid Sequence↗
PubMed1990

Pelvic floor damage and childbirth: a neurophysiological study.

Ninety six nulliparous women were investigated to establish whether childbirth causes damage to the striated muscles and nerve supply of the pelvic floor. The techniques used were concentric needle electromyography (EMG), pudendal nerve conduction tests and assessment of pelvic floor contraction using a perineometer. There was EMG evidence of re-innervation in the pelvic floor muscles after vaginal delivery in 80% of those studied. Women who had a long active second stage of labour and heavier babies showed the most EMG evidence of nerve damage. Forceps delivery and perineal tears did not affect the degree of nerve damage seen. We conclude that vaginal delivery causes partial denervation of the pelvic floor (with consequent re-innervation) in most women having their first baby. In a few this is severe and is associated with urinary and faecal incontinence. For some it is likely to be the first step along a path leading to prolapse and/or stress incontinence.

Action Potentials↗
PubMed1990

Ethylene: receptors and action.

The characterisation and purification of the ethylene binding protein from developing cotyledons of Phaseolus vulgaris is described. Polyclonal antibodies to this protein recognise homologous proteins in peas, tomatoes and Arabidopsis. Direct binding assays and results from immunological studies indicate that more binding protein is present in abscission zones of Phaseolus than in petioles; ethylene treatment increases binding site abundance in abscission zones. Binding sites for ethylene in peas. Arabidopsis and rice are described indicating that there exist two classes differing only in their rate constants of association and dissociation. Arabidopsis mutants wholly insensitive to ethylene may be receptor deficient and their possible use in receptor studies is assessed. It is proposed that those binding sites with high rate constants of association are functional receptors. The sites with low rate constants of association may be receptors but may also represent receptor precursors or internalised receptors.

Antibodies↗