Search PubMed⌕ Search

Biomedical subjects

R James

Publications and source records attributed to R James.

At least 73 records · Page 4Linked to original sources
PubMed2000

Traumatic subcutaneous translocation of the spleen in an Old English sheepdog.

A 14-month-old entire male Old English sheepdog was presented with a slowly enlarging subcutaneous soft tissue swelling caudal to the last rib. Radiographic and ultrasonographic Investigations demonstrated a soft tissue mass closely adherent to the body wall, with a coarse hypoechoic pattern. Surgical exploration revealed a mass with the gross appearance of splenic tissue. The mass was adhered to a healed paracostal abdominal tear. Histological examination confirmed the resected tissue to be normal spleen.

Abdominal Injuries↗
PubMed2000

The dose-related effects of bolus esmolol on heart rate and blood pressure following laryngoscopy and intubation.

Many researchers have studied esmolol and its effects on heart rate and blood pressure. All studied relatively large doses of esmolol. Therefore, the purpose of the present study was to determine whether small doses of esmolol would blunt the transient increases in blood pressure and heart rate caused by laryngoscopy. This double-blind, prospective, randomized study included 61 subjects. The subjects were randomized to 1 of 3 groups: group 1 received esmolol, 0.2 mg/kg; group 2 received esmolol, 0.4 mg/kg; and group 3 received saline placebo. Groups 1 and 2 had smaller increases in heart rate than group 3. We also found that the 0.4 mg/kg dose significantly blunted the increase in mean arterial pressure seen in group 3. This study shows that small doses of esmolol may block the increases in heart rate and blood pressure resulting from laryngoscopy and intubation.

Adolescent↗
PubMed1999

Structural parsimony in endonuclease active sites: should the number of homing endonuclease families be redefined?

Homing endonucleases are classified into four families based on active site sequence motifs. Through structural comparisons we have found structural similarities between the endonuclease domain of colicin E9, an H-N-H motif-containing enzyme, and both the non-specific nuclease from Serratia and I-PpoI, a His-Cys box-containing homing endonuclease. Our comparison identifies conservation at the heart of all three enzyme active sites and so argues for a re-classification of H-N-H and His-Cys box homing endonucleases as a single family. We suggest the 'betabetaalpha-Me family' of homing enzymes to reflect the three elements of secondary structure and the metal ion that define the motif.

Amino Acids↗
PubMed1999

Homing in on the role of transition metals in the HNH motif of colicin endonucleases.

The cytotoxic domain of the bacteriocin colicin E9 (the E9 DNase) is a nonspecific endonuclease that must traverse two membranes to reach its cellular target, bacterial DNA. Recent structural studies revealed that the active site of colicin DNases encompasses the HNH motif found in homing endonucleases, and bound within this motif a single transition metal ion (either Zn(2+) or Ni(2+)) the role of which is unknown. In the present work we find that neither Zn(2+) nor Ni(2+) is required for DNase activity, which instead requires Mg(2+) ions, but binding transition metals to the E9 DNase causes subtle changes to both secondary and tertiary structure. Spectroscopic, proteolytic, and calorimetric data show that, accompanying the binding of 1 eq of Zn(2+), Ni(2+), or Co(2+), the thermodynamic stability of the domain increased substantially, and that the equilibrium dissociation constant for Zn(2+) was less than or equal to nanomolar, while that for Co(2+) and Ni (2+) was micromolar. Our data demonstrate that the transition metal is not essential for colicin DNase activity but rather serves a structural role. We speculate that the HNH motif has been adapted for use by endonuclease colicins because of its involvement in DNA recognition and because removal of the bound metal ion destabilizes the DNase domain, a likely prerequisite for its translocation across bacterial membranes.

Bacterial Proteins↗
PubMed1999

Rapid folding with and without populated intermediates in the homologous four-helix proteins Im7 and Im9.

The kinetics and thermodynamics of the folding of the homologous four-helix proteins Im7 and Im9 have been characterised at pH 7.0 and 10 degrees C. These proteins are 60 % identical in sequence and have the same three-dimensional structure, yet appear to fold by different kinetic mechanisms. The logarithm of the folding and unfolding rates of Im9 change linearly as a function of urea concentration and fit well to an equation describing a two-state mechanism (with a folding rate of 1500 s-1, an unfolding rate of 0. 01 s-1, and a highly compact transition state that has approximately 95 % of the native surface area buried). By contrast, there is clear evidence for the population of an intermediate during the refolding of Im7, as indicated by a change in the urea dependence of the folding rate and the presence of a significant burst phase amplitude in the refolding kinetics. Under stabilising conditions (0.25 M Na2SO4, pH 7.0 and 10 degrees C) the folding of Im9 remains two-state, whilst under similar conditions (0.4 M Na2SO4, pH 7.0 and 10 degrees C) the intermediate populated during Im7 refolding is significantly stabilised (KUI=125). Equilibrium denaturation experiments, under the conditions used in the kinetic measurements, show that Im7 is significantly less stable than Im9 (DeltaDeltaG 9.3 kJ/mol) and the DeltaG and m values determined accord with those obtained from the fit to the kinetic data. The results show, therefore, that the population of an intermediate in the refolding of the immunity protein structure is defined by the precise amino acid sequence rather than the global stability of the protein. We discuss the possibility that the intermediate of Im7 is populated due to differences in helix propensity in Im7 and Im9 and the relevance of these data to the folding of helical proteins in general.

Amino Acid Sequence↗
PubMed1999

Preliminary X-ray crystallographic analysis of the complex between the DNAase domain of colicin E9 and its cognate immunity protein.

We have crystallized and performed preliminary X-ray characterization of the complex between the DNAase domain of the E9 colicin and its cognate immunity protein Im9. The dissociation constant for this complex, Kd = 1 x 10(-16) M, reveals it to be one of the highest affinity protein-protein interactions known. Single crystals of the 1:1 complex were grown from microseeding experiments using PEG 4K as precipitant. The space group is P212121 with one molecule of complex in the asymmetric unit, and crystals contain approximately 43% solvent. These crystals are inherently non-isomorphous and so selenomethionine-derivatized protein has been prepared and crystals grown for MAD phasing experiments.

Bacterial Proteins↗
PubMed1999

European Lipoprotein Club: report of the 21st Annual Conference, Tutzing, September 28-October 1, 1998.

Molecular biology and genetics were the hallmarks of the conference. Attendees from 20 European countries participated in lively discussions with international speakers. The opening round table session entitled 'Genetic approach to complex diseases' was chaired by Harald Funke. Steve Humphries (London) presented association studies and Harald Funke (Munster) presented multiparameter analyses, as models of genetic epidemiological approaches to atherosclerosis. Gerd Utermann (Innsbruck) showed, through sib pair linkage analysis, how apo (a) gene polymorphism determines plasma levels of Lp(a). Klaus Lindpainter (Basel) described novel genetic strategies heading for a more targeted medicine, through the identification of genetic mechanisms of disease and therapeutic responses. Session I, chaired by Richard James (Geneva) and Guido Franceschini (Milano), on 'Basic mechanisms of action of drugs' highlighted molecular and cellular actions by which present (fibrates, statins) or future (ACAT or MTP inhibitors) drugs or hormones may modulate lipoprotein metabolism. Marten Hofker (Leiden) and Philippa Talmud (London) chaired Session II on 'Regulation of gene expression', which reported cellular regulations by nuclear receptors (PPARs), or the regulation of lipid trafficking by membrane receptors (SR-BI, Megalin, Apo-E receptor, scavenger receptors) or by intracellular (IFN gamma signalling pathways) or extracellular proteins (lipases). Beyond gene expression, Session III, 1st part, entitled 'Lipoprotein modifying enzymes' was chaired by Katriina Aalto-Setälä (Tampere). Roles of lipases (HL, LPL) and transfer proteins (CETP, PLTP), as well as structures of lipid binding molecules (LCAT, apolipoproteins), were further explored. The 'Gene interactions' session chaired by Rudolph Poledne (Prague), and 'Novelties' chaired by Hans Dieplinger (Innsbruck), reported elegant models of cross-bred, tissue specific knock-out or YAC-transgenic mice for lipoprotein metabolism, and descriptions of gene interactions in polygenic disorders or new loci for familial lipid disorders (familial combined hyperlipidemia, metabolic syndrome and Tangier disease) in humans.

Animals↗
PubMed1999

Raltitrexed (Tomudex) concomitant with radiotherapy as adjuvant treatment for patients with rectal cancer: preliminary results of phase I studies.

Radiotherapy, either alone or in combination with chemotherapy, may reduce local recurrence of rectal cancer following surgery and improve survival of patients with operable and advanced/recurrent/inoperable disease. Chemotherapy with 5-fluorouracil in combination with radiotherapy has been used both before and after surgery; however, the optimum schedule is unclear. In addition, alternative chemotherapy with raltitrexed (Tomudex) may be more convenient and better tolerated. The preliminary results of three phase I dose-finding studies are described, combining escalating doses of raltitrexed with radiotherapy as pre- or postoperative treatment for operable rectal cancer or as treatment for advanced/inoperable/recurrent rectal cancer. The recommended dose of raltitrexed when combined with adjuvant radiotherapy is likely to be 2.6 mg/m2. This is a small dose reduction compared with the dose of raltitrexed for the treatment of advanced colorectal cancer (3.0 mg/m2); however, toxicity appears to be lower using the pre-operative approach. Neo-adjuvant therapy with raltitrexed plus radiotherapy also demonstrated clinical activity in the pre-operative study, which showed that 22% of patients achieved a complete response and 56% a partial response. Once the recommended dose has been defined in each setting, large-scale studies will be undertaken as appropriate.

Aged↗
PubMed1999

Structural and mechanistic basis of immunity toward endonuclease colicins.

The crystal structure of the cytotoxic endonuclease domain from the bacterial toxin colicin E9 in complex with its cognate immunity protein Im9 reveals that the inhibitor does not bind at the active site, the core of which comprises the HNH motif found in intron-encoded homing endonucleases, but rather at an adjacent position leaving the active site exposed yet unable to bind DNA because of steric and electrostatic clashes with incoming substrate. Although its mode of action is unorthodox, Im9 is a remarkably effective inhibitor since it folds within milliseconds and then associates with its target endonuclease at the rate of diffusion to form an inactive complex with sub-femtomolar binding affinity. This hyperefficient mechanism of inhibition could be well suited to other toxic enzyme systems, particularly where the substrate is a polymer extending beyond the boundaries of the active site.

Amino Acid Sequence↗
PubMed1999

Methotrexate resistance conferred by transplantation of drug-resistant transgenic marrow cells fractionated bycounterflow elutriation.

Introduction of genes conferring drug resistance into hematopoietic cells may allow for improved chemotherapy by protection of normally drug-sensitive cells from the toxic side-effects of antitumor agents. We recently reported that transplantation of murine marrow transgenic for drug-resistant dihydrofolate reductase (DHFR) protected mice from lethal doses of methotrexate (MTX), demonstrating the feasibility of imparting drug resistance to recipients of marrow expressing drug-resistant DHFR activity. In order to optimize this strategy it is necessary to identify the hematopoietic cell populations which mediate drug resistance. For this purpose, we separated committed progenitor populations from primitive hematopoietic cells in DHFR transgenic marrow by counterflow elutriation (CE). As expected, supplementation with a fraction containing committed progenitors afforded protection from MTX-induced aplasia observed early after transplantion in animals administered MTX. In contrast, supplementation with a fraction containing primitive hematopoietic cells depleted of committed progenitors failed to provide immediate protection from early aplasia, but instead contributed to drug resistance 4 to 5 weeks after transplantation. The presence of primitive hematopoietic progenitors in both fractions was evident from Southern hybridization analysis for donor transgenic cells 2 months post-transplant. We conclude that protection from aplasia associated with MTX administration immediately after transplantation requires expression of drug-resistant DHFR activity in more differentiated, committed hematopoietic cells, while primitive DHFR transgenic progenitors contribute to long-term drug resistance. These results help to define the appropriate target cells for improved chemotherapy by protection of hematopoietic cells through the introduction of new genes conferring drug resistance.

Animals↗
PubMed1999

Childhood deaths and cargo barriers in cars.

To analyse features of childhood deaths associated with the absence or presence of car cargo barriers, three cases were taken from the files of the Department of Histopathology at the Women's and Children's Hospital and State Forensic Science Centre, Adelaide, Australia, over a 5-year period from January 1993 to December 1997. Case 1: A 6-year-old boy who was a rear passenger sustained fatal crush injuries from unrestrained luggage moving forward after an accident. No cargo barrier was in place. Cases 2 and 3: Two children aged 3 and 9 years, respectively, died from acute hyperthermia after they became trapped in the back of a station wagon with a fixed cargo barrier in place. Although car cargo barriers are excellent devices for preventing injury from unrestrained objects striking or crushing passengers, designing barriers that can be opened easily from the rear of the cabin would prevent children being trapped in potentially dangerous circumstances.

Accidents, Traffic↗
PubMed1999

A critical examination of the application of the Transtheoretical Model's stages of change to dietary behaviours.

This paper proposes that the application of the Transtheoretical Model's stages of change to dietary behaviours may be fundamentally problematic due to the difference in nature between dietary behaviours and the addictive behaviours upon which the model was originally based. It was considered that specific problems associated with stage categorization for dietary change would include: problems due to the potential mismatch between a person's perceived and actual dietary behaviour; and problems due to the use of specific time periods to distinguish between different stages. A total of 541 volunteers completed questionnaires that measured their stage of change with respect to one of three dietary behaviours (healthy eating, eating a low-fat diet, and eating five portions of fruit and vegetables per day). Results indicate that people who were actively making a change (actors) or maintaining a change (maintainers) had done so for a range of different periods of time, with no specific cut-off point being evident. Also, more realistic stage categorizations were evident for the most specific dietary behaviours where there was least likelihood of a mismatch between perceived and actual dietary behaviour. Problems associated with issues of operationalization of the model and the application of the stage model to dietary change are discussed.

Adolescent↗
PubMed1999

Posttraumatic diaphragmatic hernia and death--etiologic factor or putrefactive artifact?

Late-presenting diaphragmatic hernias, whether congenital or acquired, may remain clinically undetected until mediastinal shift with cardiorespiratory compromise or intestinal or gastric infarction with perforation occur. A right-sided diaphragmatic hernia with herniation of small intestine into the adjacent pleural cavity is described in a 72-year-old man who was found dead at home in a putrefactive state. Subsequently, a history of a motor vehicle accident 8 years previously was obtained. Although postmortem herniation due to extensive putrefactive change may have occurred, producing gaseous distention and migration of the intestine, tight twisting of the herniated intestine several times around a pleural fibrous adhesion suggested that the herniation could have been an antemortem event. Unfortunately, marked tissue autolysis prevented assessment of possible ischemic changes in the herniated intestine. Although diaphragmatic hernia may be a contributing factor to death at all ages, it may not be possible to exclude it as an artifact of putrefaction in a predisposed individual.

Aged↗
PubMed1999

Pathologic features of farm and tractor-related fatalities in children.

A study of 15 childhood fatalities due to farm or tractor-related accidents demonstrated extensive injuries typified by crushing, evisceration, and amputation of limbs. Although these injuries are characteristic of industrial accidents in adults, such accidents do not commonly occur in children. However, the unique circumstance of the farm, which incorporates home and industrial environments, results in particularly severe patterns of injuries in accidental childhood deaths. A knowledge of the range of machines that are used and the environment of the farm facilitates assessment of the types of injuries that may be found at autopsy in cases of pediatric farm accident.

Accidents, Occupational↗