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Biomedical subjects

B Dawson

Publications and source records attributed to B Dawson.

At least 19 recordsLinked to original sources
PubMed1991

Identification of N-formylnorcocaine and N-benzoylnormethylecgonine in illicit cocaine.

Gas chromatographic determination of the acidic and neutral components of illicit cocaine indicated the presence of one or more common components in different samples. Isolation and examination of the spectroscopic properties of the major impurity indicated it to be N-formylnorcocaine. The material was compared with authentic material synthesized from norcocaine. N-Benzoylnormethylecgonine was also found to be present in illicit cocaine.

Cocaine↗
PubMed1991

Localization of human platelet autoantigens to the cysteine-rich region of glycoprotein IIIa.

The object of this study was to further localize autoantigenic structures on IIb-IIIa and, if possible, to precisely identify the epitopes recognized by human autoantibodies. In this paper, we identify a 50-kD chymotryptic fragment of IIIa that is recognized by a high percentage of human autoantibodies, typified by the prototype IgG autoantibody RA, which binds to IIIa on intact platelets as well as in an immunoblot assay under nonreduced conditions. Using an immunoblot assay, a carboxy-terminal region of this fragment (33 kD) that contains the cysteine-rich domains of IIIa was found to carry the epitope(s) recognized by the prototype autoantibody RA. The amino-terminal amino acid sequence of the reduced 33-kD fragment, the smallest fragment that retains the RA epitope, is XPSQQDEXSP, and that of the reduced 50-kD fragment is IVQVTFD. This indicates that the 33-kD fragment consists of approximately 175 amino acids beginning at residue 479 and extending at least through residues 636-654, while the 50-kD fragment spans the same region but begins at residue 427. It is apparent that the 33-kD fragment is generated from the 50-kD fragment by additional chymotryptic hydrolysis but remains associated because of the multiple disulfide bonds that are characteristic of this cysteine-rich domain. Sera from 48% of patients with chronic ITP and 2 of 8 patients with acute ITP contain antibodies that bind to the 50-kD fragment in an ELISA. Antibodies of the same specificity are also found in one-third of patients with either secondary immune thrombocytopenia or apparent non-immune thrombocytopenia. We conclude that the 50-kD cysteine-rich region of IIIa is a frequent target of autoantibodies in ITP, but that such antibodies may also be present in cases of thrombocytopenia that cannot be linked to an apparent autoimmune process.

Autoantibodies↗
PubMed1989

Improvements in heat tolerance induced by interval running training in the heat and in sweat clothing in cool conditions.

To compare the effectiveness of training in heat and in sweat clothing in cool conditions on improving heat tolerance, two groups of active subjects (n = 6 in each) performed an interval running heat-tolerance test before and after a 7-day experimental treatment. On each treatment day the subjects attempted to complete 4 x 15 min interval treadmill running periods (a 7.5 s effort every 30 s, on 15 km h-1, 15% grade; the same exercise format as the heat-tolerance test), which were interspersed with 5-min recovery periods (total time each day = 80 min). Group 1 (heat) ran in shorts, socks and shoes in hot humid conditions, and Group 2 (sweat clothing) ran in cool conditions dressed in shorts, socks and T-shirt covered by a polyester-cotton tracksuit, over which was worn 100% nylon spray-proof pants and jacket (cotton lined) with an acrylic cloth bobble hat (beanie) on the head. Both groups displayed changes typical of heat acclimatization over the 7-day period, with significant decreases in final rectal temperature (Tr) and heart rate (HR) being evident, but no change in sweat loss. Mean skin temperature (Tsk) was similar in both groups during the training sessions (heat group: 34.8-35.7 degrees C; sweat clothing group 34.9-35.5 degrees C). After the heat-tolerance test, both groups had significantly lower Tr, Tsk and HR values than before, and sweating sensitivity (g m-2 h-1 degrees C rise in Tr) was significantly increased. There was only one significant difference between the two groups (Tsk, 20th min value). It was concluded that training in sweat clothing in cool conditions can provide the same improvements in heat tolerance as training in hot humid conditions where a fixed exercise intensity and duration are used.

Acclimatization↗
PubMed1987

The effects of age, epinephrine, and operative site on duration of caudal analgesia in pediatric patients.

The effects of age, operative site (penoscrotal or inguinal), and the addition of epinephrine 1:200,000 to bupivacaine on duration of postoperative analgesia after caudal block were prospectively and blindly evaluated in 341 children aged 13 months to 17 yrs. At the conclusion of the surgical procedures under halothane/N2O/O2 anesthetics (n = 419), caudal blocks were performed with 0.5 ml/kg of either 0.25% bupivacaine or 0.25% bupivacaine with 1:200,000 epinephrine injected at a rate of 0.5 ml/sec. The duration of analgesia was noted by parents or nurses who had been instructed how to identify, in a standard manner, the onset of postoperative pain. The mean duration of analgesia was significantly longer in young children (P less than 0.001), in children having penoscrotal operations (P less than 0.001), and when epinephrine was added to bupivacaine (P less than 0.001). There were no major complications. The authors conclude that duration of analgesia is significantly influenced by age, operative site, and the addition of epinephrine 1:200,000 to bupivacaine.

Age Factors↗
PubMed1986

Encoding contour shape by curvature extrema.

Curvature extrema provide significant information about the shape of an image contour, such as a silhouette, and are the basis for the Hoffman-Richards codon representation for shape. This representation based on curvature easily translates into a binary string that will describe the abstract shape of any smooth image curve. The computation of the basic shape primitives requires dealing with two ever-pervasive problems: contour noise and scale. We show how contour noise can be estimated given knowledge of the shape of the filter used to compute curvature from the edge list of the contour. To handle the scale problem, we use an adaptation of Witkin's scale space. Our algorithm differs from Witkin's by using a notion of parts to set criteria for significant structures.

Algorithms↗
PubMed1985

The effect of BW 540C, a novel anti-inflammatory agent, on ultraviolet-induced physical and histological changes in guinea-pig skin.

We have examined the effects of various topical formulations of BW 540C, a novel dual inhibitor of the cyclo-oxygenase and lipoxygenase pathways of arachidonic acid metabolism, utilizing the model of ultraviolet irradiation of guinea-pig ears. During a series of studies, BW 540C preparations were compared with a range of corticosteroids, a cyclo-oxygenase inhibitor and a placebo using both subjective and objective measurements. Results showed BW 540C base to be the best overall agent for treating the pathological changes seen in this model.

Administration, Topical↗
PubMed1985

A multidisciplinary diagnostic/genetic study on the 105 patients with mental retardation of the E.S. Le Grange School.

A comprehensive genetic/diagnostic survey was undertaken at a special school for the mentally retarded involving 105 patients. Cytogenetic, biochemical and clinical investigations were undertaken to establish the contribution of the genetic factors to the problem of mental retardation. Apart from obtaining information about specific children, identifying families at risk, and providing genetic counselling in nearly 50% of cases, data was obtained which could be compared with other similar surveys. According to the aetiological groupings of the patients, 6.7% could be attributed to perinatal damage, 17.1% to chromosomal defects, 4.8% to biochemical disorders, 5.7% to other genetic causes, 12.4% to other prenatal damage, 1.9% to infections, and 51.4% to unknown causes. No individual with the marker X syndrome was found in this group.

Adolescent↗
PubMed1983

Pheochromocytoma in the pediatric age group: current status.

Pheochromocytoma is an unusual tumor in the pediatric age group. Several aspects serve to differentiate children with pheochromocytoma from their adult counterparts. Children have fewer malignant tumors, more extraadrenal tumors, and greater bilaterality and multiplicity of tumor. Similarly, they have an increased incidence of multiple endocrine neoplasia (MEN) and familial disease. The records of 16 children (age 17 years and younger) with pheochromocytoma were evaluated. One newborn died at 36 hours of age, and a 3-year-old died four days after exploratory laparotomy. Of the 14 survivors (with an average follow-up of 8 years), three had manifestations of multiple endocrine neoplasia type 2 and two had familial pheochromocytoma only. One patient had malignant paragangliomas. Three patients had bilateral tumors; one of these had MEN. Four patients underwent operation before the use of alpha- and beta-adrenergic blockade was routine at our institution. An additional patient received blockade in preparation for the removal of the pheochromocytoma but was not prepared for preoperative angiography. Hypertensive complications were encountered in four of these five children; in one, this complication was fatal. There were no intraoperative complications in the 12 patients who had received appropriate blocking agents. Eleven of the 14 survivors are currently normotensive without the need for antihypertensive medication. Two patients have medically controlled hypertension, and one continues to have severe hypertension. An overview of this series underscores the characteristic features of pheochromocytoma in the pediatric age group. Angiography has been replaced by high-resolution computed tomography for localization.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1981

PBB inhibits metabolic cooperation in Chinese hamster cells in vitro: its potential as a tumor promoter.

Using an in vitro assay system, polybrominated biphenyl (PBB) was assessed for its ability to inhibit metabolic cooperation between 6-thioguanine sensitive and resistant Chinese hamster V79 cells. Using a nonlethal range of the chemical, PBB was shown to inhibit metabolic cooperation (a form of cell-cell communication) in a manner similar to other known tumor promoters. Results suggest that PBB could act, epigenetically, as a teratogen and a carcinogenic promoter.

Animals↗
PubMed1979

Reduced ferrochelatase activity in fibroblasts from patients with porphyria variegata.

Ferrochelatase deficiency has been shown in both porphyria variegata (PV) and erythropoietic protoporphyria (EPP). It has been suggested that in PV there is a decrease in the enzyme, whereas in EPP the enzyme is unstable. In the present study ferrochelatase activity was measured in skin fibroblasts from three patients with PV and three normal subjects. The enzymatic activity in the patients with PV (17.5 +/- 4.5 pmoles heme formed per 10(7) fibroblasts per hour) was 50% of that of the control group (31.0 +/- 3.2 pmoles heme formed per 10(7) fibroblasts per hour). This supports the contention that the enzyme is deficient in PV and that an inactive ferrochelatase is the primary deficiency in this type of porphyria.

Fibroblasts↗
PubMed1979

X;15 translocation in a retarded girl: X inactivation pattern and attempt to localise the hexosaminidase A and other loci.

Cytogenetic studies on a retarded girl showed a complex S;15 translocation, karyotype 45,X,-15,+t(X15). The translocation X chromosome was non-randomly partially inactivated, the inactivation being mainly confined to the X segment and in some cells only to the X long arm. Gene marker studies failed to show anomalous segregation of the hexosaminidase A gene or any other gene markers tested.

Abnormalities, Multiple↗
PubMed1978

Structure of human luteinizing hormone alpha subunit.

Structural studies have substantiated the concept that the glycoprotein hormones consist of a "common" alpha subunit and "hormone-specific" beta subunit. Despite this, consensus is still lacking concerning certain portions of the amino acid sequences, including alignment of residues 81--82 in the alpha subunit. We have carried out sequence analysis of the alpha subunit of human luteinizing hormone (hLH) to clarify the assignment of these residues and to examine further the nature of the amino-terminal heterogeneity found among the different alpha subunits. Our structure showed residues 80--84 to be -His-Cys-Ser-Thy-Cys-, consistent with findings of others for human follicle stimulating hormone (hFSH) and human chorionic gonadotropin (hCG). The extensive degree of heterogeneity found in the amino terminal region of hFSH and hCG is present to only a minor extent in hLH. The differences in the pattern of amino-terminal heterogeneity among the various hormones may result from differences in the nature of cleavage of subunit from a larger intracellular precursor peptide.

Amino Acid Sequence↗