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Biomedical subjects

M Ryan

Publications and source records attributed to M Ryan.

At least 163 records · Page 9Linked to original sources
PubMed1997

Bordetella pertussis-specific Th1/Th2 cells generated following respiratory infection or immunization with an acellular vaccine: comparison of the T cell cytokine profiles in infants and mice.

In an investigation of cell-mediated immunity against Bordetella pertussis, we found that B. pertussis infection in infants and in mice was associated with the induction of antigen-specific T cells that secrete IFN-g and IL-2, but not IL-4 or IL-5. This cytokine profile is characteristic of Th1 cells that mediate cellular immune responses against a range of intracellular pathogens. An examination of cytokine production following immunization with a three-component acellular vaccine, comprising inactive PT, FHA and pertactin adsorbed to alum, demonstrated that spleen cells from vaccinated mice produced high levels of IL-5, but no detectable IFN-g and low levels of IL-2. In contrast, peripheral blood mononuclear cells from vaccinated infants produced IL-2, IL-5 and IFN-g. These findings highlight significant differences in the immune responses generated by vaccination and natural infection with B. pertussis and demonstrate that the T-cell response induced with an acellular vaccine, although dominated by type 2 cytokines in mice, is more heterogeneous in infants with a Th0 or mixed Th1/Th2 cytokine profile.

Adult↗
PubMed1996

Synthesis, structure-activity relationships, and the effect of polyethylene glycol on inhibitors of phosphatidylinositol-specific phospholipase C from Bacillus cereus.

Substrate analog inhibitors of Bacillus cereus phosphatidylinositol-specific phospholipase C (PI-PLC) were synthesized and screened for their suitability to map the active site region of the enzyme by protein crystallography. Analogs of the natural substrate phosphatidylinositol (PI) were designed to examine the importance of the lipid portion and the inositol phosphate head group for binding to the enzyme. The synthetic compounds contained pentyl, hexyl, or hexanoyl and octyl lipid chains at the sn-1 and sn-2 positions of the glycerol backbone and phosphonoinositol, phosphonic acid, methyl phosphonate, phosphatidic acid, or methyl phosphate at the sn-3 position. The most hydrophobic compound, dioctyl methyl phosphate 14, was also the best inhibitor with an IC50 of 12 microM. In a series of dihexyl lipids, compounds with phosphonoinositol head groups inhibited more strongly than those that do not contain inositol but are otherwise identical. Compound 29, a short-chain lipid with a phosphonoinositol head group, was found to be a competitive inhibitor and the most potent in this series with an IC50 of 18 microM (Ki = 14 microM). Analogs with dihexyl chains were better inhibitors than those with dihexanoyl chains, presumably because the ether-linked lipids are more hydrophobic than the ester-linked lipids. No appreciable difference in inhibition was found between a phosphonoinositol lipid and the corresponding difluorophosphonoinositol lipid. Inositols and inositol derivatives that do not contain lipid moieties show IC50s about 3 orders of magnitude above those of the short-chain lipids. In this group, glucosaminyl(alpha 1-->6)-D-myo-inositol inhibited more strongly than myo-inositol, which in turn is a better inhibitor than inositol phosphate. The addition of polyethylene glycol (PEG-600) resulted in a marked decrease in inhibition by the short-chain lipids, but had little effect on the water-soluble head group analogs. This is accounted for in terms of solubilization of the amphipathic inhibitors by PEG. Since PEG is required in the crystallization, these data indicate that the best strategy for obtaining enzyme inhibitor complexes is to start by cocrystallizing PI-PLC with the head group analogs. The next step is to synthetically add the shortest possible hydrophobic moieties to the analogs and cocrystallize these with the enzyme. This strategy may be applicable to other lipolytic enzymes.

Bacillus cereus↗
PubMed1996

Crystal structure of phosphatidylinositol-specific phospholipase C from Bacillus cereus in complex with glucosaminyl(alpha 1-->6)-D-myo-inositol, an essential fragment of GPI anchors.

Numerous proteins on the external surface of the plasma membrane are anchored by glycosylated derivatives of phosphatidylinositol (GPI), rather than by hydrophobic amino acids embedded in the phospholipid bilayer. These GPI anchors are cleaved by phosphatidylinositol-specific phospholipases C (PI-PLCs) to release a water-soluble protein with an exposed glycosylinositol moiety and diacylglycerol, which remains in the membrane. We have previously determined the crystal structure of Bacillus cereus PI-PLC, the enzyme which is widely used to release GPI-anchored proteins from membranes, as free enzyme and also in complex with myo-inositol [Heinz, D.W., Ryan, M. Bullock, T.L., & Griffith, O. H. (1995) EMBO J. 14, 3855-3863]. Here we report the refined 2.2 A crystal structure of this enzyme complexed with a segment of the core of all GPI anchors, glucosaminyl(alpha 1-->6)-D-myo-inositol [GlcN-(alpha 1-->6)Ins ]. The myo-inositol moiety of GlcN(alpha 1-->6)Ins is well-defined and occupies essentially the same position in the active site as does free myo-inositol, which provides convincing evidence that the enzyme utilizes the same catalytic mechanism for cleavage of PI and GPI anchors. The myo-inositol moiety makes several specific hydrogen bonding interactions with active site residues. In contrast, the glucosamine moiety lies exposed to solvent at the entrance of the active site with minimal specific protein contacts. The glucosamine moiety is also less well-defined, suggesting enhanced conformational flexibility. On the basis of the positioning of GlcN(alpha 1-->6)Ins in the active site, it is predicted that the remainder of the GPI-glycan makes little or no specific interactions with B. cereus PI-PLC. This explains why B. cereus PI-PLC can cleave GPI anchors having variable glycan structures.

Bacillus cereus↗
PubMed1996

Heat-resistant factors in human erythrocyte membranes mediate CD4-dependent fusion with cells expressing HIV-1 envelope glycoproteins.

It has been shown that human CD4 expressed in nonhuman cells does not support HIV-1 entry into those cells and that components from human cells in addition to CD4 are required to overcome the block. We have used human red blood cells (huRBC) as a source for the accessory components since their membrane composition is less complex than that of nucleated cells and they are well characterized. Components were transferred by fusion of huRBC to nonhuman CD4(+) cells mediated by influenza hemagglutinin or polyethylene glycol. The RBC-modified nonhuman CD4(+) cells were labeled with fluorescent markers and incubated with gp 120-gp41-expressing cells labeled with a different fluorescent probe. Fusion between RBC- modified nonhuman CD4(+) cells and gp 120--gp41-expressing cells was quantified by fluorescence video microscopy. Human erythrocyte components transferred to nonhuman CD4+ cells conferred HIV-1 envelope glycoprotein-mediated fusion susceptibility to those cells. The fusion was enhanced by pretreatment of the erythrocytes for 10 min at 56 degrees. No gp 120--gp41-mediated fusion was observed when components from nonhuman RBC were transferred to nonhuman CD4+ cells. Human cell lines with pre-RBC characteristics (K562-CD4) also supported HIV-1 envelope glycoprotein-mediated fusion.

Animals↗
PubMed1996

Genetic variation in bilirubin UPD-glucuronosyltransferase gene promoter and Gilbert's syndrome.

BACKGROUND: The genetic basis of Gilbert's syndrome is ill-defined. This common mild hyperbilirubinaemia sometimes presents as an intermittent jaundice. A reduced hepatic bilirubin UPD- glucuronosyltransferase (UGT) is associated with this syndrome. We have examined variation in the gene encoding the UGT1*1 enzyme and serum bilirubin levels in a Scottish population. METHODS: Blood was collected from 12 patients with confirmed or suspected Gilbert's syndrome, from 6 members of a family with 4 Gilbert members, and from 77 non-smoking, alcohol-free, drug-free volunteers recruited from the staff of a teaching hospital in Dundee. Polymerase chain reaction amplification was used to examine sequence variation of the promoter upstream of the UGT1*1 exon I. Genotypes were assigned as follows: 6/6 (homozygous for a common allele bearing the sequence [TA](6)TAA), 7/7 (homozygous for a rarer allele with the sequence [TA](7)TAA), and 6/7 (heterozygous with one of each allele). FINDINGS: Individuals in the population with the 7/7 genotype had significantly higher bilirubin concentrations than those who had the 6/7 or 6/6 genotype. 14 volunteers underwent a 24 h fasting test to see if they had Gilbert's syndrome, and all four positives had the 7/7 genotype. One confirmed Gilbert's patient, two recurrent jaundice patients (with suspected Gilbert's syndrome), and nine clinically diagnosed cases had the 7/7 genotype. Segregation of the 7/7 genotype with the Gilbert phenotype was also demonstrated in the family with four affected members. The frequency of the 7/7 genotype in this eastern Scottish population was 10-13%. INTERPRETATION: In a healthy population there was an association between variation in bilirubin concentration and a mutation within the gene encoding the enzyme bilirubin UGT. This and other findings suggest the existence of a mild and a more severe form of Gilbert's syndrome, depending on whether the gene defect lies in the promoter sequence upstream of UGT1*I exon I, as here (mild), or in the coding sequence (severe) of the gene.

Adult↗
PubMed1996

Dependence of tissue oxygen on oxygen delivery.

The viability of tissue flaps depends on adequate blood flow and oxygenation. To help ensure oxygen delivery, increased inspired oxygen is often provided. This study uses a porcine model to measure tissue oxygen (TPO2) in a muscle flap, in response to varying levels of inspired oxygen concentration (FiO2). Six swine underwent the creation of a latissimus dorsi island flap. An ultrasonic flow probe was used to monitor afferent flow through the thoracodorsal artery, and a 20-ga fluorescence-quenching optode was employed to monitor TPO2. Additional optodes were inserted in muscle of an ipsilateral hindlimb, and in the terminal ileum. Inspired oxygen concentration was varied from 15 to 100%, and oxygen delivery variables measured. Analysis of variance and multiple linear regression were used to determine which variables had the greatest effect on TPO2. All three sites varied directly with inspired oxygen concentration. Flap TPO2 had a strong dependence on FiO2 and local oxygen delivery (r2 = 0.54). PaO2 and hemoglobin were the most significant determinants of ileal submucosal TPO2 (r2 = 0.65). A correlation between average submucosal and flap TPO2 was observed (r > 0.9, P < 0.05). We conclude that (1) muscle flap and bowel TPO2 vary directly with inspired FiO2, (2) changes in ileal submucosal TPO2 correlate with those observed in muscle, and (3) monitoring of readily accessible muscle TPO2 merits further investigation to evaluate the status of TPO2 in critical visceral beds.

Animals↗
PubMed1996

Surgical outcome in acquired immunodeficiency syndrome patients with non-Hodgkin's lymphoma of the gastrointestinal tract.

PURPOSE: Incidence of non-Hodgkin's lymphoma (NHL) has shown a dramatic increase, concurrent with the epidemic of acquired immunodeficiency syndrome (AIDS). In terms of surgical intervention, management of the patient with AIDS-NHL remains unclear. Purpose of this paper was to determine the role and outcome of surgical intervention in patients with AIDS-NHL of the gastrointestinal (GI) tract. METHODS: Data were obtained by retrospective chart review. RESULTS: From 1980 to 1993, charts of 22 patients with diagnosis of AIDS-NHL of the GI tract who underwent either biopsy or surgical procedure were reviewed. All patients were male, with a mean age of 35.7 years. Sixty-seven biopsies were performed in the 22 patients identified. No morbidity or mortality was associated with any of the biopsy procedures. Major intra-abdominal operations were performed in eight patients, including seven who underwent primary resections of lymphomas. Mean survival for the group as a whole was 18 months, although that for the seven patients undergoing resection was 20.4 months. CONCLUSIONS: Diagnosis of AIDS-NHL of the GI tract should not discourage performance of otherwise appropriate surgical procedures.

Adult↗
PubMed1996

New stone formation: a comparison of extracorporeal shock wave lithotripsy and percutaneous nephrolithotomy.

PURPOSE: There is theoretical concern that stone recurrence rates may be higher following extracorporeal shock wave lithotripsy (ESWL) compared to other techniques because of residual stone debris. MATERIALS AND METHODS: We documented all new stone formations in 298 consecutive patients who initially achieved a stone-free status following ESWL for renal calculi less that 2 cm in largest dimension, and compared the findings to those of 62 patients treated with percutaneous nephrolithotomy without ultrasonic fragmentation. Stone-free status was assessed by a centrally reviewed plain abdominal film and renal tomograms at 3 months. A plain abdominal film was repeated at 12 and 24 months to detect recurrence. RESULTS: New stones formed in 22.2% of patients after ESWL and 4.2% after percutaneous nephrolithotomy at 1 year (p = 0.004), and in 34.8% versus 22.6%, respectively, at 2 years (p =0.190). Furthermore, more new stones recurred in the lower and mid calices compared to baseline location in the ESWL group (chi-square <0.0001), which was not observed in the percutaneous nephrolithotomy group. CONCLUSIONS: Our data support a trend toward higher stone recurrence rates in ESWL treated patients, which may be due to microscopic sand particles migrating to dependent calices and acting as a nidus for new stone formation.

Female↗
PubMed1996

Circadian relationships between circulating atrial natriuretic peptides and serum calcium and phosphate in healthy humans.

Long-acting natriuretic peptide (LANP), vessel dilator (VSDL), and atrial natriuretic factor (ANF) consisting of amino acids (aa) 1 to 30, 31 to 67, and 99 to 126, respectively, of the 126-aa ANF prohormone circulate in humans. Among the biologic properties of these peptides is the ability of ANF to decrease intracellular calcium concentrations. To determine if atrial natriuretic peptides are directly related to serum calcium and/or phosphate in healthy normocalcemic humans, we examined 21 24-hour profiles of VSDL, LANP, ANF, and serum calcium and phosphate in 14 healthy humans. VSDL, LANP, and ANF each had significant (P < .001) circadian rhythms, with peak concentrations late during sleep (at 4:00 AM) being nearly twice the concentrations in the afternoon and evening. Serum calcium and phosphate also had significant circadian rhythms (P < .001) with troughs nearly opposite to those of the atrial natriuretic peptides, suggesting that atrial peptides may be important in the modulation of the circadian rhythms of calcium and phosphate. The nearly identical circadian rhythms of the atrial natriuretic peptides and of parathyroid hormone (PTH) reported by others, along with evidence that PTH may increase atrial peptide release, suggest that some of the effects attributed to PTH may be mediated by atrial natriuretic peptides.

Adult↗
PubMed1996

The organisms reported to cause infective myocarditis and pericarditis in England and Wales.

It is difficult to acquire an overall perspective of the range of organisms responsible for infective myocarditis or pericarditis, and their relative importance, as most studies have involved only case reports or case series of a single organism. This study analyses reports to the Communicable Disease Surveillance Centre, of the Public Health Laboratory Service. Reports where myocarditis or pericarditis was included as the main clinical features between 1990 and 1993 were studied. Between 1990 and 1993, 368 cases of myocarditis and/or pericarditis were reported to CDSC. Viruses were reported to cause 253 (69%) cases, bacteria were responsible for 49 (13%) cases, mycoplasma for 32 (9%) cases, chlamydia for 16 (4%) cases and Mycobacterium tuberculosis for nine (2%) cases. Infection with coxsackie B virus was most frequently associated with a mixed picture of myo/pericarditis, whereas influenzae virus was associated with pericarditis or myocarditis alone. This information will provide clinicians with details of the more likely pathogens responsible for these conditions.

England↗
PubMed1996

The use of magnetic resonance imaging to assess swelling after the removal of third molar teeth.

OBJECTIVE: To assess the suitability and accuracy of magnetic resonance imaging (MRI) in measuring the swelling of the face and lingual tissues after removal of third molar teeth. DESIGN: Prospective open study. SETTING: Teaching hospital, Scotland. SUBJECTS: 5 patients 19-22 years old with bilateral mesioangular impacted wisdom teeth. INTERVENTIONS: Magnetic resonance imaging scans taken before, and 1 and 7 days after, removal of bilateral lower wisdom teeth under general anaesthesia. MAIN OUTCOME MEASURES: Amount of swelling measured postoperatively compared with preoperatively. Coefficient of analytical variation calculated for the main observer, and between him and a second observer to assess accuracy and reproducibility for each examiner and between examiners. RESULTS: Buccal swelling on the first postoperative day was significantly greater than preoperative (P < 0.01). There was no significant difference in lingual swelling. The mean coefficient of variation for the first examiner was 1.92 and there was no significant difference between the two examiners. CONCLUSIONS: Measurements on MRI scans are both recordable and reproducible for buccal swelling, but lingual swelling is more difficult to measure because of problems in defining the lateral border of the tongue. MRI scans provide an objective measurement of swelling after extraction of wisdom teeth and could be used to evaluate the efficacy of drug regimens.

Adult↗
PubMed1996

Estimating the economic benefits of avoiding food-borne risk: is 'willingness to pay' feasible?

In this paper, the results of a pilot study of willingness to pay (WTP) to avoid poultry-borne illness are reported. Through this, the problems of devising an economic measure of the 'intangible' benefits of prevention of food-borne risk are explored. The study is the first to allow those against a prevention policy (irradiation of poultry-meat) to register their WTP not to have the policy implemented. The study demonstrates that it is feasible to obtain answers to WTP questions from a self-selected sample. Future studies should ensure greater representativeness of respondents, that better information about benefits is provided to respondents and that an appropriate method of aggregation of benefits is used.

Adult↗
PubMed1996

Recognition of foot-and-mouth disease virus and its capsid protein VP1 by bovine peripheral T lymphocytes.

The role of T cells in immunity to foot-and-mouth disease virus is still poorly defined compared to that of the humoral response. In this paper we describe a systematic, longitudinal study on the cellular recognition of FMDV and its subunit protein VP1 by bovine peripheral blood T lymphocytes. Multiple vaccination with a single virus serotype induced a serotype cross-reactive proliferative T cell repertoire that varied in magnitude between individual animals and with the serotype of the vaccine used. Primary proliferative T cell responses of vaccinated and acutely infected cattle were weak relative to the magnitude of responses determined for the same animals after boosting. In contrast, the level of circulating antibody produced after both primary and secondary exposure to virus was good. Phenotypic analysis of lymphocytes from vaccinated or infected cattle showed a small increase in CD8+ T cells after infection compared to vaccination. However, in general the profiles of circulating lymphocytes elicited were similar. Thus, we were not able to use proliferative or phenotypic analyses to distinguish between vaccinated and convalescent cattle. T cell recognition of VP1 by multiply-vaccinated cattle was serotype-specific implying that the cross-reactive responses observed with whole virus may be attributed to proteins other than VP1. In contrast to other studies, immunization with recombinant VP1 induced only low levels of neutralizing antibody and failed to elicit profound proliferative responses or protection ever after two immunizations.

Animals↗
PubMed1996

The costs of treating miscarriage: a comparison of medical and surgical management.

OBJECTIVES: To estimate and compare the costs of surgical and medical treatment of miscarriage to the National Health Service. DESIGN: A patient-centred, partially randomised trial. SETTING: A teaching hospital in Scotland. PARTICIPANTS: Four hundred and thirty-seven women with a proven first trimester miscarriage. MAIN OUTCOME MEASURES: The cost per patient of surgical and medical management of miscarriage plus the extra cost per patient of introducing medical management of miscarriage under three different scenarios are calculated. RESULTS: The average cost of surgical treatment was Pounds 397 compared with Pounds 347 for medical treatment. Sensitivity analysis showed that the extra cost of introducing the medical management of miscarriage ranged from a cost saving of Pounds 71 per patient to an additional cost of Pounds 47 per patient. CONCLUSIONS: Our analysis showed that it may be possible to generate cost savings by introducing medical methods in the management of early miscarriage. However, the savings assume that costs associated with theatre use can be fully realised.

Abortion, Induced↗
PubMed1996

Signal transduction in Pneumocystis carinii: characterization of the genes (pcg1) encoding the alpha subunit of the G protein (PCG1) of Pneumocystis carinii carinii and Pneumocystis carinii ratti.

Pneumocystis carinii is a eukaryotic organism that causes pneumonia in immunocompromised hosts. The cell biology and life cycle of the organism are poorly understood primarily because of the lack of a continuous in vitro cultivation system. These limitations have prevented investigation of the organism's infectious cycle and hindered the rational development of new antimicrobial therapies and implementation of measures to prevent exposure to the organism or transmission. The interaction of P. carinii with its host and its environment may be critical determinants of pathogenicity and life cycle. Signal transduction pathways are likely to be critical in regulating these processes. G proteins are highly conserved members of the pathways important in many cellular events, including cell proliferation and environmental sensing. To characterize signal transduction pathways in P. carinii, we cloned a G-protein alpha subunit (G-alpha) of P. carinii carinii and P. carinii ratti by PCR amplification and hybridization screening. The gene encoding the G-alpha was present in single copy on a 450-kb chromosome of P.c. ratti. The 1,062-bp G-alpha open reading frame is interrupted by nine introns. The predicted polypeptide showed 29 to 53% identity with known fungal G-alpha proteins with greatest homology to Neurospora crassa Gna-2. Northern (RNA) blot analysis and immunoprecipitation demonstrated expression of the G-alpha mRNA and protein P. carinii isolated from heavily infected animals. Some alteration in the level of transcription was noted in short-term maintenance in starvation or rich medium. Characterization of signal transduction in P. carinii will permit a better understanding of the reproductive capacity and other cellular processes in this family or organisms that cannot be cultured continuously.

Amino Acid Sequence↗
PubMed1996

Circadian relationships between circulating atrial natriuretic peptides and serum sodium and chloride in healthy humans.

Long-acting natriuretic peptide (LANP), vessel dilator (VSDL), and atrial natriuretic factor (ANF) consisting of amino acids 1-30, 31-67, and 99-126 of the 126 amino acid ANF prohormone, respectively, circulate in humans and have potent natriuretic properties. To determine whether these peptides have a direct relationship to serum Na and/or Cl, we examined 21 24-hour profiles of these peptides and Na and Cl in 14 healthy humans. LANP, VSDL, ANF, and Cl had significant (p < 0.001) circadian rhythms with peak concentrations at 04.00 h. The circadian rhythm of serum Na was exactly opposite. Sodium correlated negatively with LANP (p = 0.021) and ANF (p = 0.007), while Cl correlated positively with LANP (p = 0.003) and VSDL (p = 0.001). These data suggest that the atrial peptides may be important for the maintenance of serum Na and Cl within their normal ranges and in the modulation of their daily circadian rhythms.

Adult↗