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S Williamson

Publications and source records attributed to S Williamson.

At least 19 recordsLinked to original sources
PubMed1992

Mimicry of elastin repetitive motifs by Theileria annulata sporozoite surface antigen.

Theileria annulata is an important pathogen of cattle in the tropics. The gene sequence of a sporozoite surface antigen (SPAG-1) is reported. Data is also presented demonstrating that SPAG-1 is synthesised as a large precursor. This antigen, which is a candidate for inclusion in a subunit vaccine, shows a remarkable degree of molecular mimicry to the extracellular matrix protein elastin. It contains both repetitive motifs PGVGV and VGVAPG. Immunofluorescence using a monoclonal antibody against VGVAPG confirmed that this peptide is expressed on sporozoites as predicted. The presence of VGVAPG is particularly interesting since this is the ligand for elastin receptors on a range of cell types, including macrophages/monocytes which are a major class of host target cells. It is proposed that this antigen represents the ligand whereby T. annulata recognises its host cells.

Amino Acid Sequence↗
PubMed1991

Abnormal processing of affective words by psychopaths.

We tested the hypothesis that psychopathy is associated with abnormal processing of affective verbal material. Criminal psychopaths and nonpsychopaths, defined by the Psychopathy Checklist, performed a lexical decision task ("Is it a word or not?") while we recorded reaction time and event-related potentials in response to letter-strings consisting of affective and neutral words and pronounceable nonwords. On the assumption that they do not make efficient use of affective information, our primary prediction was that psychopaths would show less behavioral and event-related potential differentiation between affective and neutral words than would nonpsychopaths. The results were in accordance with this prediction. The lexical decisions of nonpsychopaths were significantly faster, and relevant event-related potential components were significantly larger, to affective words than to neutral words. In sharp contrast, psychopaths failed to show reaction time facilitation or larger amplitude event-related potentials to affective words. We suggest that psychopaths extract less information from affective words than do other individuals. Possible implications of these and related findings for understanding the behavior of psychopaths are discussed.

Adolescent↗
PubMed1990

The adenohypophysis of the Australian lungfish, Neoceratodus forsteri--an immunocytological study.

The cell types in the adenohypophysis of Neoceratodus resemble closely those already described for Lepidosiren and Protopterus. Four of these were immunocytochemically identified as prolactin cells, gonadotropes, corticotropes, and melanotropes. Antiserum to bullfrog growth hormone could not distinguish between prolactin cells and somatotropes. Anti-bullfrog prolactin, however, did selectively stain the prolactin cells, which allowed the identification of the somatotropes. The presumptive thyrotropes, as the only remaining cell type in the pars distalis, can then be tentatively identified by default. Likewise a PAS-positive cell type in the pars intermedia had no immunoreactivity to any of the antisera used. The functional significance of this cell remains to be demonstrated. One of the more unexpected findings was the presence of large numbers of cells immunoreactive to alpha-MSH in the proximal pars distalis. The implications of the presence of these cells in adult lungfish are discussed. The distribution of cell types within the pituitary of Neoceratodus showed more regionalization than is present in the other lungfish and corresponded more closely to that described for primitive actinopterygian fish. The general structure of the pituitary of Neoceratodus also resembled primitive actinopterygian fish more closely than it did amphibians, unlike the pituitaries of Lepidosiren and Protopterus. The evolutionary significance of this is also discussed.

Adrenocorticotropic Hormone↗
PubMed1990

Urinary growth hormone excretion as a screening test for growth hormone deficiency.

Overnight urinary growth hormone secretion was measured by an immunoradiometric assay incorporating commercially available reagents, in 41 normal prepubertal school-children from three age groups: 3-5 years, 6-7 years, and 9-10 years. There was no significant difference between the groups expressing the results as total microU/specimen and so they have been combined to provide a prepubertal reference range of 2.25-10.50 microU/night. Prepubertal children with growth hormone deficiency who had not been receiving growth hormone treatment for two days had overnight urinary growth hormone concentrations well below this range. Urinary growth hormone was assayed in 49 children undergoing investigation for short stature with conventional provocative testing, and those shown to have growth hormone deficiency had correspondingly low overnight urinary growth hormone concentrations. There was, in addition, a strong correlation between overnight urinary growth hormone concentrations and peak serum response to provocation. This simple urine assay may provide a useful screening test for growth hormone deficiency.

Adolescent↗
PubMed1990

Influence of caffeine administered during pregnancy on the early differentiation of fetal rat ovaries and testes.

In this manuscript it is demonstrated that caffeine when administered to the rat (30 mg/kg per day) during pregnancy affected certain aspects of normal sexual differentiation of the fetal gonads. In the male fetus caffeine was shown to significantly inhibit differentiation of the interstitial tissue and Leydig cells. A significant decrease in the number of Leydig cells exhibiting 3 beta-hydroxysteroid dehydrogenase activity, and consequent reduction in testosterone biosynthesis in the fetal testes at day 15 and day 16 of gestation was found. While the beginnings of Leydig cell function was first seen in the afternoon of the 14th day of gestation in both the experimental and control groups, the adverse effects became marked by 15 days and extreme by 16 days. With the aid of the scanning electron microscope it was observed that caffeine also had an effect on the earlier morphogenic organisation of the seminiferous cords at 13 days of gestation where the aggregation of the Sertoli cells forming the seminiferous cords, was marginally advanced in the control group. However the treated group had caught up by 14 days of gestation. In the female fetus scanning electron microscope studies revealed that in the control and caffeine treated groups the early phase of ovarian differentiation and the later 20 day ovaries were similar in morphology, tissue arrangement and overall appearance. It was also seen that chronic caffeine exposure did not affect the rate of early mitotic proliferation of germ cells, nor later in development the numbers entering meiosis. At 20 days of gestation the numbers and proportion of meiotic to atretic oocytes were comparable in the control and treated groups.(ABSTRACT TRUNCATED AT 250 WORDS)

3-Hydroxysteroid Dehydrogenases↗
PubMed1989

Theileria annulata sporozoite surface antigen expressed in Escherichia coli elicits neutralizing antibody.

Theileria annulata is an economically important protozoan parasite that threatens an estimated 250 million cattle with the disease tropical theileriosis. Development of a defined subunit vaccine is one means of trying to develop control measures against the disease. To this end we have characterized a surface antigen complex of the infective stage (sporozoite), by using a monoclonal antibody that neutralizes sporozoite infectivity in vitro. We have cloned the gene coding for this complex and have demonstrated that a fusion protein expressed from a fragment of this gene elicits strong neutralizing antibodies. Furthermore we provide data on the structure and expression of this gene. In particular we show that the region of the gene, expressed in one clone, codes for a protein segment relatively rich in proline residues. Also we demonstrate that expression of this gene appears to be stage specific, transcripts being present only in the sporoblast and sporozoite stages. The relevance of these findings to the production of a defined subunit vaccine is discussed.

Amino Acid Sequence↗
PubMed1988

Neutrophil lactoferrin content: variation among mammals.

Lactoferrin (Lf) in blood and/or marrow neutrophils was semiquantified using indirect immunofluorescence technique in nine mammalian species. Neutrophil iron-binding reactivity (NFeBR), which corresponds primarily to Lf, was also visualized and semiquantified using functional cytochemical (FeNTA-AF) technique at the light microscopic level in these nine and in an additional fifteen mammalian species, and in selected species at the ultrastructural level. Neutrophil immunoreactive Lf was positively correlated with total cellular and granule content of NFeBR among these nine species, and with previously reported concentrations of neutrophil Lf quantified by radioimmunoassay. Relative levels of Lf in neutrophil extracts from rat, hamster, and human were confirmed using SDS-polyacrylamide gel electrophoresis and immunoblotting. Relatively high levels of immunoreactive neutrophil Lf and/or NFeBR were observed in carnivores (ten species) and primates (six species). Among rodents (five species), the levels were variable, and the artiodactyls (four species) studied had low levels. These results demonstrate that neutrophil Lf levels vary widely among mammalian species. In addition, FeNTA-AF technique provides a rapid means of evaluating animals for relative quantities of neutrophil Lf.

Animals↗
PubMed1988

Concentrated drinking water extracts, which cause bacterial mutation and chromosome damage in CHO cells, do not induce sex-linked recessive lethal mutations in Drosophila.

Concentrated extracts prepared from chlorinated drinking water samples were tested for their ability to induce sex-linked recessive lethal mutations in Drosophila melanogaster. Adult flies were allowed to feed on sucrose solutions prepared using neat or half-strength water extract. The drinking water extracts used for this study were also tested in bacterial fluctuation assays using Salmonella typhimurium TA100 and TA98 and in an in vitro cytogenetic assay using CHO cells. Although the water extracts gave positive results in both of these in vitro tests, there was no evidence of mutagenic activity in the Drosophila studies.

Animals↗
PubMed1987

Ultrasonography in the diagnosis of pyloric stenosis.

We evaluated 101 children for hypertrophic pyloric stenosis (HPS) at Arkansas Children's Hospital. Diagnosis was based upon a palpable epigastric "olive" characteristic of HPS, or sonographic measurements of the pylorus. In 28 children, the diagnosis was confirmed by physical examination alone; the remaining 73 had ultrasound examination. Pyloric measurements included muscle thickness, transverse diameter, and total length. Pyloric function was also studied during examination. Using a thickness of less than 4 mm, a diameter of less than 13 mm, and a length of less than 17 mm as normal criteria, 31 cases of HPS were correctly diagnosed by ultrasonography. In the remaining 42, no pyloric abnormality could be demonstrated on further evaluation.

Evaluation Studies as Topic↗
PubMed1986

Mutagenic activity of concentrated drinking water samples.

Concentrated drinking water extracts prepared by adsorption onto XAD-2 resin have been tested for their ability to induce chromosome damage in mammalian cells. Extracts prepared from drinking waters derived from upland and lowland sources have been found to induce chromosome aberrations in Chinese hamster ovary (CHO) cells and human lymphocytes in vitro. Although the identity of the compounds responsible for this activity is unknown, they are generated when the water is chlorinated and appear to bind readily to exogenous protein. When groups of mice were dosed orally with a concentrated water extract, however, no evidence of clastogenic activity in bone marrow cells was apparent. The absence of an in vivo effect may indicate that the mutagenic compounds failed to reach the bone marrow. The possibility that genetic damage could be induced in the cells first encountered in the body after ingestion (i.e., cells in the esophagus, stomach, and intestinal tract) is not precluded by this result. The relevance of these findings in evaluating the potential health hazard of mutagenic compounds in drinking water is discussed.

Animals↗
PubMed1986

Engraftment rates related to busulphan and cyclophosphamide dosages for displacement bone marrow transplants in fifty children.

The use of busulphan and cyclophosphamide permitted engraftment in 44 of 49 children receiving 'displacement' bone marrow transplants. Three patients who received T-cell-depleted marrow cells from HLA-haploidentical donors failed to engraft and other graft failures were due to inadequate induction dosage. Our standard schedule comprises busulphan 80 mg/m2/day x 4 days (adjusted if necessary to a minimum of 4 mg/kg/day or a maximum of 5 mg/kg/day) followed by cyclophosphamide 2 g/m2/day x 4 days but reduced so as not to exceed 75 mg/kg/day, a maximum dose preferred for patients with full marrows (e.g. those with thalassaemia major). Of 21 recipients of mixed lymphocyte culture (MLC)-negative donor marrow cells with full engraftment at 100 days, there were three late rejections. Of patients transplanted with marrow from MLC-positive donors, one had late rejection after cyclosporin A toxicity had necessitated withdrawal of the drug at day + 146 but six other patients, whose cyclosporin A was stopped routinely 1 year, remain well with full grafts. Ten patients died as a result of graft-versus-host disease. We are therefore exploring new approaches to T-cell depletion and storing autologous marrow for use in the event of graft failure. If necessary, a second transplant with busulphan and cyclophosphamide is best performed at 3 months after full recovery of the host. We conclude that elective transplants can be performed successfully in children with normal immune function without the need for irradiation.

Bone Marrow↗
PubMed1985

Use of donors sharing one genetic haplotype for bone marrow transplantation.

Matched sibling transplants enjoy over 95% survival of the grafting procedure, but are only available for 1:5 patients. A sibling sharing one genetic haplotype is today our next choice of donor (67% survival) faring better than other relatives (50% survival), providing total body irradiation (of the thymus) has been avoided. The latter, without increasing the attack rate (64%) of GvHD more than doubles the deaths (57% as against 27%) attributable to it. Rejection is avoided by (a) suicide of host responders to donor buffy coat; (b) Cyclosporin-A; (c) displacement induction; (d) a higher dose of marrow. Prevention of GvHD is essential, using either Cyclosporin-A or removing donor T-cells from marrow prior to infusion or, probably better, both. Autoblast immunisation should be further explored. Tolerization seems an active process, easier in the very young, and nonirradiation of the thymus is believed important. An assay to assess tolerization (to guide cessation of immunosuppressive measures) is badly needed. Selection of a donor whose lymphocytes can deal with intracellular infections of the host's fibroblasts is now possible. The required increased immunosuppressive measures appear to increase the risk of leukemic relapse, and perhaps should be first improved in the more cost-effective fields of inborn error transplants.

Bone Marrow Transplantation↗