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Biomedical subjects

T Jackson

Publications and source records attributed to T Jackson.

At least 91 records · Page 5Linked to original sources
PubMed1995

Aortic aneurysm morphology for planning endovascular aortic grafts: limitations of conventional imaging methods.

PURPOSE: To test whether conventional computed tomography scanning (CT) and contrast aortography (CA) provide adequate data for planning endovascular aortic grafting by measuring 33 parameters in patients having both imaging examinations for evaluation of abdominal aortic aneurysms (AAA). METHODS: Fifty consecutive patients with AAA (41 men, 9 women; average age 65 years) had CT and CA (mean 26 days between exams). The data collected and analyzed included: 8 sites of diameter, 4 lengths, 6 angles, and 15 other dimensional measurements. RESULTS: Conflicts between CA and CT data were common. Eighteen patients appeared to have a distal cuff by CA but not by CT. Proximal neck length could not be assessed by CT in 5 and had a difference between CA and CT > 1 cm in 25 patients. CA overestimated neck length in 11 patients. Common iliac artery angulation > 60 degrees unilaterally in 27 patients and bilaterally in 5. Seven patients had both iliac aneurysm and > 60 degree iliac angulation. Thirteen patients had one or more iliac aneurysms (> 2 cm) shown by CT but not by CA. CONCLUSIONS: For endovascular graft planning: (1) more detailed measurement is required than for traditional surgery; and (2) conventional CT and CA are complementary imaging studies, but each has important limitations.

Aged↗
PubMed1995

Effects of instruction on a divided visual-field task of face processing.

The purpose of the present study was to document that instruction effects can occur on tasks typically yielding left visual-field advantages. In a lateralized face-recognition task, 40 right-handers (20 men, 20 women) had to memorize pairs of faces and to respond to a probe face displaying positive or negative emotion and presented for 100 msec. 3.8 degrees on the left or right of a fixation cross. Half of the subjects had been instructed to learn the faces through a verbal strategy and the other half through an imagery strategy. Analysis of reaction times yielded significant complex interactions involving gender, coding instruction, visual field, and emotion for both Yes and No responses. A global left visual-field advantage was obtained in the analyses of accuracy and sensitivity data, but no significant effects were recorded in the analysis of decision rule. Thus, the instruction effects on left visual-field advantages were obtained through complex interactions on reaction times only. Further replication of these data would provide a more secure basis for causal interpretations.

Attention↗
PubMed1995

Casemix: the building blocks.

This paper distinguishes three separate ways in which casemix measurement serves as a foundation for hospital and health system reform. At the hospital level, diagnosis related groups provide a means of describing kinds of acute inpatient care which in turn facilitates utilisation review activities essential to modern clinical and financial management. At the system level, casemix adjusters such as diagnosis related groups provide the basis for comparisons of productive efficiency across institutions, and reduce the risk of adverse funder reactions to higher per case costs which are attributable to differences in casemix. States are increasingly using casemix as the basis for funding hospitals in order to reduce non-casemix related differences. Finally, health reform experiments in using market-like mechanisms (such as managed competition, purchaser-provider split) require at a minimum that the product purchased be precisely specified, and that clinical risks of cost overruns be equalised amongst insurers or providers.

Australia↗
PubMed1995

A randomised single institution study comparing laser prostatectomy and transurethral resection of the prostate.

We concluded a prospective randomised study comparing conventional electrocautery transurethral resection of the prostate (TURP) to laser prostatectomy using a right-angled Nd:YAG beam reflector. Seventy-one patients were evaluable, 34 laser and 37 TURP. Fifty patients have completed 6 months of follow-up. Using standard post prostatectomy outcome parameters of maximum flow rate and post void residual urine, laser prostatectomy shows equivalence at 6 months, with mean maximum flow rates of 8.76 ml/sec preoperatively improving to 15.47 ml/sec at 6 months, whilst for TURP patients, flow rates improved from a mean of 9.48 ml/sec preoperatively to 19.1 ml/sec at 6 months. Symptom scores remain higher for the laser patients at this time with a mean score of 9.27 compared to 4.43 for TURP patients. However, morbidity in the laser group is less, particularly given the absence of postoperative bleeding and the necessity for blood transfusion.

Aged↗
PubMed1995

Reading grade levels and health behaviors of parents at child clinics.

OBJECTIVES: Recent reports suggest alarmingly low levels of literacy among adults in the U.S., but these are not expressed in grade levels. Assessment of the epidemiology of reading grade levels is necessary for development of patient education materials written at appropriate levels. METHODS: We measured demographics, reading ability and self-described health behaviors of 646 parents at two private, two university, two indigent and six public child-related clinics in a midwestern city using a bilingual oral interview and the Wide Range Achievement Test. RESULTS: Parents were 59% white, 92% female, with mean age 28 years, mean years of school 12.1 and mean reading grade 8.7. Parents tended to read four to five grades below their highest completed school grade. Analysis of self-reported health behaviors showed that 69% had no private insurance, 31% smoked cigarettes, 35% had body mass index greater than 27, and 46% of parous mothers had never breast-fed. Prevalence odds ratios showed that all adverse health risks except obesity were associated with low reading ability. CONCLUSIONS: These findings have important implications for public health professionals working in clinical care, health education and agency policy. Persons with low literacy levels appear to be at particularly high risk for adverse health behaviors. Education materials and teaching vocabulary should be appropriate for client reading grade levels.

Adolescent↗
PubMed1995

Cyanide poisoning in two donkeys.

In November 1994 2 donkeys died acutely in a pasture at Danby, New York. At necropsy at the New York State College of Veterinary Medicine, Cornell University, no significant gross or histopathological lesions were found in either donkey. After the death of the second donkey, a toxic cause was suggested. Stomach contents submitted for toxicologic analysis from the second donkey were positive for cyanide. Together with the history and clinical signs, this result provided the basis for a diagnosis of cyanide poisoning in these donkeys.

Animals↗
PubMed1994

Activation of phosphoinositide 3-kinase is required for PDGF-stimulated membrane ruffling.

BACKGROUND: There is substantial evidence that phosphoinositide 3-kinase (PI 3-kinase) is a critical component of signalling pathways used by the cell-surface receptors for a variety of mammalian growth factors and other hormones. The physiological product of this enzyme is a highly polar membrane lipid called phosphatidylinositol (3,4,5)-trisphosphate This lipid has been postulated to act as a second-messenger in cells but its putative targets are still unknown. RESULTS: A particular rearrangement of actin filaments, which results in membrane ruffling, is elicited by the activation of PDGF beta-receptors expressed in cultured porcine aortic endothelial cells. We have found that this consequence of PDGF beta-receptor activation is inhibited by three independent manipulations of PI 3-kinase activity: firstly, by the deletion of tyrosine residues in the PDGF beta-receptor to which PI 3-kinase binds; secondly, by the overexpression of a mutant 85 kD PI 3-kinase regulatory subunit to which the catalytic kinase subunit cannot bind; and thirdly, by the addition of the fungal metabolite wortmannin, which is a potent inhibitor of the catalytic activity of PI 3-kinase. CONCLUSIONS: These results argue strongly that phosphatidylinositol (3,4,5)-trisphosphate synthesis is required for growth-factor-stimulated membrane ruffling in porcine aortic endothelial cells, and suggest that synthesis of this lipid may be part of a signalling pathway leading to direct or indirect activation of the small GTP-binding protein Rac.

Androstadienes↗
PubMed1994

Characterization of a phosphatidylinositol-specific phosphoinositide 3-kinase from mammalian cells.

BACKGROUND: As phosphoinositides can serve as signalling molecules within cells, the enzymes responsible for their synthesis and cleavage are likely to be involved in the transduction of signals from the cell surface through the cytoplasm. The precise role of the phosphoinositide 3-kinase that has been cloned from mammalian cells is not known, but it has been implicated in receptor-stimulated mitogenesis, glucose uptake and membrane ruffling. The enzyme can use phosphatidylinositol (PtdIns), PtdIns 4-phosphate and PtdIns (4,5)-bisphosphate as substrates in vitro, but it seems to phosphorylate PtdIns (4,5)-bisphosphate preferentially in vivo. The VPS34 gene product of yeast, by contrast, is a phosphoinositide 3-kinase homologue implicated in vacuolar protein sorting that apparently utilizes only PtdIns as a substrate. The significance of this difference in lipid-substrate preference and its relationship to the functions of the two phosphoinositide kinases is unknown. RESULTS: We have characterized a distinct PtdIns-specific phosphoinositide 3-kinase activity in mammalian cells. Unlike the previously identified, broad-specificity mammalian phosphoinositide kinase, this enzyme is resistant to the drug wortmannin and uses only PtdIns as a substrate in vitro; it therefore has the capacity to generate PtdIns 3-phosphate specifically. The newly characterized enzyme, which was purified by chromatography from cytosol, has biochemical and pharmacological characteristics distinct from those of the broad-specificity enzyme. CONCLUSIONS: The enzyme we have characterized may serve to generate PtdIns 3-phosphate for fundamentally different roles in the cell from those of PtdIns (3,4)-bisphosphate and/or PtdIns (3,4,5)-trisphosphate. Furthermore, the functions of the VSP34 gene product, which may not be relevant to the broad-specificity mammalian phosphoinositide 3-kinase, may be related to those of the enzyme we describe.

Amino Acid Sequence↗
PubMed1994

The structure of an immunodominant loop on foot and mouth disease virus, serotype O1, determined under reducing conditions.

Residues 136-159 of VPI of foot and mouth disease virus (FMDV) comprise the G-H loop of the protein and form a prominent feature on the surface of virus particles. This sequence contains an immunodominant neutralizing epitope, which can be mimicked with synthetic peptides, and includes an Arg, Gly, Asp motif which has been implicated in the binding of the virus to cellular receptors. Crystallographic analysis of native virus particles failed to resolve the structure of this region due to its disordered state. However, reduction of a disulphide bond between cysteine residues 134 of VP1 and 130 of VP2 caused the G-H loop to collapse onto the surface of the virus particle and allowed its conformation to be determined.

Amino Acid Sequence↗
PubMed1993

Synthesis of phosphatidylinositol 3,4,5-trisphosphate in permeabilized neutrophils regulated by receptors and G-proteins.

Formylated Met-Leu-Phe (fMLP), platelet-activating factor (PAF), ATP, and various nonhydrolyzable guanine nucleotides stimulated accumulation of phosphatidylinositol 3,4,5-trisphosphate (PtdIns(3,4,5)P3) in intact human neutrophils. A protocol was devised to selectively inhibit the capacity of the nucleotide-sensitive receptors to elicit accumulation of PtdIns (3,4,5)P3. This enabled study of the regulation of phosphoinositide 3OH-kinase (PI3K) activities in permeabilized neutrophils free from interference due to activation of cell-surface nucleotide receptors. FMLP, PAF, and nonhydrolyzable GTP analogues stimulated an increase in the concentration, and rate of synthesis, of PtdIns(3,4,5)P3 in permeabilized neutrophils by increasing the rate of a PtdIns(4,5)P2-directed PI3K-catalyzed reaction. A number of characteristics of these responses, including their relative sensitivities to inhibition by pertussis toxin and guanosine 5'-beta-(thio)diphosphate, suggested that fMLP and PAF increased this PI3K activity via the actions of heterotrimeric G-proteins. Basal and guanosine 5'-gamma-(thio)triphosphate/fMLP-stimulated increases in PI3K activity were resistant to changes in free calcium concentrations, staurosporine, acute treatment with phorbol esters, and evidently to permeabilization. This, in conjunction with other work, indicates that the PAF and fMLP-induced increase in PtdIns(4,5)P2-directed PI3K activity is not being produced via activation of a currently defined G-protein regulated effector enzyme, or a protein tyrosine kinase coordinated mechanism of a type already known to regulate PI3K activities.

Adenosine Triphosphate↗
PubMed1993

Structure of a major immunogenic site on foot-and-mouth disease virus.

Attachment of foot-and-mouth disease virus (FMDV) to its cellular receptor involves a long and highly antigenic loop containing the conserved sequence, Arg-Gly-Asp, a motif known to be a recognition element in many integrin-dependent cell adhesion processes. In our original crystal structure of FMDV the Arg-Gly-Asp-containing loop ('the loop'), located between beta-strands G and H of capsid protein VP1, was disordered and hence essentially invisible. We previously surmised that its disorder is enhanced by a disulphide bond linking the base of the loop (Cys 134) to Cys 130 of VP2 (ref. 8). We report here the crystal structure of the virus in which this disulphide is reduced. Reduced virus retains infectivity and serological experiments suggest that some of the loop's internal structure is conserved. But here its structure has become sufficiently ordered to allow us to describe an unambiguous conformation, which we relate to some key biological properties of the virus.

Aphthovirus↗
PubMed1993

Receptor stimulated accumulation of phosphatidylinositol (3,4,5)-trisphosphate by G-protein mediated pathways in human myeloid derived cells.

Phosphoinositide 30H-kinase (PI3K) activities are thought to be critical regulatory enzymes in a new intracellular signalling pathway, the activation of which results in the rapid accumulation of a putative signalling molecule, phosphatidylinositol (3,4,5)-trisphosphate [PtdIns(3,4,5) P3]. To date, activation of PI3K has always correlated with its recruitment into complexes containing protein tyrosine kinases (PTK). Here we report that agonists which utilize G-protein mediated transduction pathways can stimulate very rapid and large accumulations of PtdIns(3,4,5)P3 via a novel mechanism, possibly involving direct coupling between the G-protein and a PI3K activity. In addition, some of these agonists also stimulate small increases in PI3K activity in anti-phosphotyrosine and anti-src-type PTK antibody directed immunoprecipitates, indicating activation of PI3K via a 'conventional' PTK mediated mechanism; these pathways however, play only a minor role in the initial, agonist sensitive production of PtdIns(3,4,5)P3 in myeloid derived cells.

Adenosine Triphosphate↗
PubMed1993

Outbreak of Japanese encephalitis on the island of Saipan, 1990.

During October 1990, an outbreak of encephalitis occurred on Saipan. Although no virus was isolated, patients seroconverted to Japanese encephalitis (JE) virus, indicating the first known occurrence of JE on US territory since 1947. Ten cases occurred among a population of 40,000. The prevalence of antibody to JE virus among 234 lifelong Saipan residents surveyed after the outbreak was 4.2%. Age, household crowding, and lack of air conditioning were risk factors for infection. The seroprevalence in pigs, which are important amplifying hosts of JE virus, was 96% (n = 52). None of 288 stored serum specimens from lifelong Saipan residents sampled in 1984 were seropositive. These data suggest that JE virus was recently introduced onto Saipan and that peridomestic factors affected the risk of human infection. Transmission of JE virus probably ended with exhaustion of the supply of susceptible amplifying hosts. Surveillance for human cases and seroconversions in pigs during 1991 revealed no evidence of ongoing JE virus transmission.

Adolescent↗
PubMed1993

Oncology nurse and physician attitudes toward aggressive cancer treatment.

Oncology nurses (n = 57) and oncology physicians (n = 40) employed in the same hospital completed the Cancer Attitude Questionnaire. Significant differences (p < or = .001) between nurse and physician attitudes were evident on the two major subscales addressing the issues of (a) aggressiveness of treatment/de-emphasis of socioemotional aspects of care and (b) the importance of patient-family attitudes. Physicians' attitudes were significantly more favorable on the first subscale; nurses' attitudes were significantly more favorable on the second. Implications of these findings as indicators of potential nurse-physician conflict are discussed.

Adult↗