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Biomedical subjects

J O'Donnell

Publications and source records attributed to J O'Donnell.

At least 37 records · Page 2Linked to original sources
PubMed2001

Elevated plasma factor VIII levels--a novel risk factor for venous thromboembolism.

An association between elevated plasma levels of FVIII:C and arterial thrombosis was first described 20 years ago. More recently a growing literature has centered on the potential role for elevated FVIII:C in venous thromboembolic disease. 25% of patients have plasma FVIII:C levels greater than 1500 IU/l six months following venous thrombosis. This increased FVIII:C appears unrelated to any ongoing acute phase reaction, and reflects a true increase in circulating FVIII protein. Furthermore the increase in FVIII:C is sustained in the vast majority of subjects for years following the thrombotic episode. Multivariate analysis of the Leiden thrombophilia study has demonstrated that increased FVIII is an independent risk factor for venous thromboembolism. Individuals with FVIII:C exceeding 1500 IU/l had a six-fold increased risk, compared to those with FVIII:C levels less than 1000 IU/l. Also, prospective follow-up has shown that patients with high FVIII:C levels are at increased risk for episodes of recurrent venous thrombosis. These findings support the theory that increased plasma levels of FVIII:C represent a constitutional prothrombotic tendency. However the mechanism underlying the elevation in FVIII remains unknown.

Factor VIII↗
PubMed2001

Undisclosed port-wine stain--anesthetic implications and psychosocial considerations: a case report.

Port-wine stains (nevus flammeus, port-wine nevus) are congenital vascular lesions that have psychological and physiological implications for patient care. The location and size of these lesions can lead to complications related to anesthetic management. Facial lesions have the most profound psychological effect on the patient with respect to behavior alterations and reluctance to disclose the lesion's presence. Covering makeup has become increasingly effective not only in concealing the lesion, but also in being nearly undetectable during routine examination. Issues such as agent choice, surgical position, frequency of positioning evaluation, and choice of intravenous fluid should be considered when caring for a patient with a port-wine stain. In this case study the authors describe the anesthesia implications and outcome in a patient who refused to disclose her port-wine lesion in the preoperative interview and who ignored preoperative instructions to remove all makeup before presenting for surgery.

Anesthesia↗
PubMed2000

Nodal quasiparticle lifetime in the superconducting state of Bi(2)Sr(2)CaCu(2)O(8+delta)

We have measured the complex conductivity sigma of a Bi(2)Sr(2)CaCu(2)O(8+delta) thin film between 0.2 and 0.8 THz. We find sigma in the superconducting state to be well described as the sum of contributions from quasiparticles, condensate, and order parameter fluctuations which draw 30% of the spectral weight from the condensate. An analysis based on this decomposition yields a quasiparticle scattering rate on the order of k(B)T/Planck's over 2pi for temperatures below T(c).

Journal Article↗
PubMed2000

Signature of superfluid density in the single-particle excitation spectrum of Bi(2)Sr(2)CaCu(2)O(8+delta)

We report that the doping and temperature dependence of photoemission spectra near the Brillouin zone boundary of Bi(2)Sr(2)CaCu(2)O(8+delta)exhibit unexpected sensitivity to the superfluid density. In the superconducting state, the photoemission peak intensity as a function of doping scales with the superfluid density and the condensation energy. As a function of temperature, the peak intensity shows an abrupt behavior near the superconducting phase transition temperature where phase coherence sets in, rather than near the temperature where the gap opens. This anomalous manifestation of collective effects in single-particle spectroscopy raises important questions concerning the mechanism of high-temperature superconductivity.

Journal Article↗
PubMed2000

Mesoscopic thermodynamics of an inhomogeneous colossal-magnetoresistive phase

Equilibrium conductivity fluctuations of mesoscopic domains are found in film and bulk single-crystal manganite colossal magnetoresistive material. Temperature and field dependences of the Boltzmann factors for a collection of two-state fluctuators give measures of the magnetic moment and entropy differences between the states, and of the fluctuator volumes. The large resistance step size implies dramatic current inhomogeneities. Occasional anomalous temperature dependences indicate that the film inhomogeneous phase is stabilized by a repulsive interaction between conducting regions.

Journal Article↗
PubMed2000

24. The Fusion of Anatomic and Physiologic Tomographic Images to Enhance Accurate Interpretation.

Purpose: Dedicated PET-(fluorine-18)-fluorodeoxyglucose (FDG) studies were interpreted with the corresponding anatomic images (MR or CT) using image fusion display to improve spatial accuracy for the interpreter and the referring physician.Methods: The image-fusion display system was designed in-house and allows manual alignment and display of one image volume as an overlay on the other which has improved accurate correlation of physiological and anatomical information for more than 50 patient studies.Results: A case of a patient with left foot recurrent melanoma is presented for which the PET scan showed a large focus of activity just lateral to the urinary bladder. Image fusion confirmed that the PET focus corresponded to an abnormal lymph node on the follow-up CT scan. In a case of bladder carcinoma which included bladder augmentation, altered surgical anatomy rendered interpretation of the FDG-PET images difficult. The fusion with the patient's CT scan allowed evaluation of the altered physiology due to the altered surgical anatomy which permitted accurate image interpretation. In a case of pelvic lymphoma, the FDG-PET scan showed intense activity adjacent to the acetabulum and possibly within it. Image fusion allowed accurate localization of the patient's primary lesion with the additional benefit of showing activity extending into the adjacent bone.Conclusion: Image fusion of tomographic, anatomic and physiologic information permits accurate lesion localization including separation of soft tissue from bone. The image-fusion technique facilitates image-guided biopsy by providing accurate anatomic localization.

Journal Article↗
PubMed2000

Bleeding symptoms and coagulation abnormalities in 337 patients with AL-amyloidosis.

Haemorrhage is a frequent manifestation of amyloidosis. We performed a retrospective clinical analysis of 337 patients with systemic immunoglobulin light-chain (AL)-amyloidosis, in whom whole-body serum amyloid P component (SAP) scintigraphy and a clotting screen had been performed. Abnormal bleeding was noted in 94 cases (28%), and the coagulation screen was abnormal in 172 cases (51%). The most common abnormalities were prolongation of the thrombin time (TT; 108 cases, 32%) and the prothrombin time (PT; 82 cases, 24%). In multivariate analysis, a prolonged PT was the only coagulation abnormality associated with abnormal bleeding (P = 0.0012), but this was independent of the whole-body amyloid load. Prolongation of the TT was associated with hepatic amyloid infiltration (P < 0.00001), with proteinuria (P < 0.001) and low serum albumin (P < 0.00001). In 154 patients who were studied further, subnormal factor X activity (FX:C) was found in 22 cases (14%). In cases with subnormal FX:C, the corresponding factor X antigen (FX:Ag) measurements were consistently higher (median FX:Ag/FX:C 2.5, range 0.81-9.25, n = 16) than cases with normal FX:C (median FX:Ag/FX:C 0.96, range 0.65-1.29, n = 28, P < 0.0001). No evidence was found of an FX inhibitor. Of the 48/154 (31%) cases with a prolonged TT, the reptilase time was also prolonged in 38/48 cases (79%). These data show that haemorrhage and abnormal coagulation are common in AL-amyloidosis and are multifactorial in origin. We provide evidence suggesting that hepatic amyloid infiltration and nephrotic syndrome are determinants of the TT. In most patients, prolongation of the PT was explained by reduction in FX:C, but this was not wholly explained by a reduction in FX:Ag.

Adult↗
PubMed2000

Lamotrigine overdose in an adult.

BACKGROUND: Lamotrigine is an antiepileptic agent that has been shown to be an effective adjunctive treatment for refractory partial and generalized seizures. It is now licensed in more than 70 countries for this indication. There is very little published material about the effects of acute overdose with lamotrigine. CASE REPORT: We describe the findings in a patient following the deliberate ingestion of a large amount of lamotrigine (stated 4.5 g, absorbed estimated 2.9 g), in excess of that previously described in the literature. The main clinical features were ataxia and rotary nystagmus. Electrocardiogram was unremarkable. Peak measured concentration of lamotrigine was 35.8 mg/L and half-life 19.5 hours, suggesting linear kinetics in overdose.

Adult↗
PubMed2000

Coronary angioplasty and stenting in orthotopic heart transplants: a fruitful act or a futile attempt?

Accelerated allograft coronary artery disease remains the major cause of mortality after the first year of transplantation. Despite the extensive use of stents and angioplasty in coronary artery disease, there is a paucity of data about the efficacy of such interventions in orthotopic heart transplants. The authors herein report the outcome of those patients in their institution who had undergone percutaneous coronary artery angioplasty and stenting at a late stage of their transplantation. Within a 12-year period, 106 adult patients underwent orthotopic heart transplantation at their institution. Eight of these patients with 17 lesions underwent deployment of nine stents and eight angioplasties 8.1 +/- 3.2 years posttransplantation. There were 15 denovo and two restenotic lesions. The indications for intervention were presence of symptoms in five patients and severity of lesions in three asymptomatic patients detected on their follow-up angiogram. All patients had angiographic worsening of lesions at their follow-up angiogram. The initial procedural success for both stented and angioplastied lesions was 100%. Within a mean angiographic follow-up of 261 days, all balloon angioplastied lesions had developed restenosis, whereas within a mean period of 67 days, 50% of stented lesions had developed restenosis. On the follow-up angiogram, deterioration of the nontreated segments were noted throughout the coronary arterial tree; however, the immediate proximal and distal parts of the target segments demonstrated an exaggerated hyperproliferative response as compared to other sites. The overall median time to the detection of restenosis for both stented and angioplastied lesions was 5.2 months (inner quartile 2.5-6.2 months). The authors conclude that angioplasty and stenting late in the course of transplantation is associated with a significant restenosis rate and in such patients earlier or alternative catheter-based interventions must be considered.

Angioplasty, Balloon, Coronary↗
PubMed2000

Stimulus control and generalization of point-loss punishment with humans.

Two experiments demonstrated stimulus control and generalization of conditioned punishment with humans. In both studies, responses first were reinforced with points exchangeable for money on a variable-interval schedule in the presence of one line length (S(D)). Next, a second line length was introduced, and point loss followed every response in the presence of that line (S(D)p). In the final training condition, points were deducted at session end. Response rate was lower in the presence of the S(D)p despite equal rates of points for money in the presence of both stimuli. In generalization testing for Experiment 1, the two lines were included in a 10-line continuum; S(D)p fell in the middle and the trained SD was at one end. Lines were presented randomly, and point delivery and loss contingencies were as in training but with points available in the presence of all lines. For all subjects, response rates were lowest around S(D)p and increased towards the SD end of the continuum. Because testing included only one or two lines beyond S(D), this pattern did not rule out S(D) generalization. Thus, in Experiment 2, stimuli beyond S(D) were added to generalization tests. Response rates did not decrease as a function of distance from S(D), clarifying the demonstration of punishment generalization.

Adult↗
PubMed2000

Pneumococcal pneumonia in patients requiring hospitalization: effects of bacteremia and HIV seropositivity on radiographic appearance.

OBJECTIVE: Our purpose was to establish the incidence of lobar versus bronchopneumonia patterns in patients hospitalized for pneumococcal pneumonia and to determine whether bacteremia or HIV status affects the radiographic appearance. MATERIALS AND METHODS: Eighty-one patients with community-acquired pneumococcal pneumonia and positive findings on admission chest radiographs were selected from a group of 105 patients with positive findings for Streptococcus pneumoniae from sputum or blood cultures. Patients less than 16 years old and those with nosocomial pneumonia, aspiration pneumonia, or coexistent lung disease were excluded. The dominant pattern was classified as lobar or lobular bronchopneumonia by two radiologists who were unaware of results from blood cultures and HIV testing. RESULTS: Forty-three females and 38 males, with a mean age of 48 years (age range, 16-92 years), required admission for pneumococcal pneumonia. Fifty-nine (73%) of the 81 patients were bacteremic and 20 (25%) of the 81 patients were HIV-positive, including 14 patients (17%) who were both bacteremic and HIV-positive. Among all the patients, focal lobar consolidation was the most common pattern, observed in 48%. Multifocal lobar consolidation was the next most frequent pattern, occurring in 33%. Multifocal and focal bronchopneumonia patterns were seen in 16% and 2% of the patients, respectively. Overall, multifocal consolidation occurred in 49%. The dominant radiographic pattern and incidence of multicentric disease were not affected by HIV seropositivity (p = 0. 61) or bacteremia (p = 0.17). CONCLUSION: Lobar consolidation, involving single or multiple lobes, is the most common radiographic pattern of community-acquired pneumococcal pneumonia in patients requiring hospitalization. The pattern of consolidation is not influenced by bacteremia or HIV status.

Bacteremia↗
PubMed2000

Functional interactions between GTP cyclohydrolase I and tyrosine hydroxylase in Drosophila.

Tyrosine hydroxylase requires the regulatory cofactor, tetrahydrobiopterin, for catecholamine biosynthesis. Because guanosine triphosphate cyclohydrolase I is the rate limiting enzyme for the synthesis of this cofactor, it has a key role in catecholamine production. We show that GTP cyclohydrolase and tyrosine hydroxylase (TH) are co-localized in the Drosophila central nervous system. Mutations in the Punch locus, which encodes GTP cyclohydrolase, reduce TH activity; addition of cofactor to crude extracts could not fully rescue this activity in all mutant strains. The decrease in TH activity and the inability to increase it with added cofactor is not due to loss or decreased production of TH protein. We found that TH co-immunoprecipitated with GTP cyclohydrolase when wild type head extracts were incubated with anti-GTP cyclohydrolase antibody. We suggest that regulation of TH by its cofactor may require its association with GTP cyclohydrolase, and that the ability of GTP cyclohydrolase to associate with TH and its role in tetrahydrobiopterin synthesis may be separable functions of this enzyme. These results have important implications for understanding catecholamine-related neural diseases and designing strategies for gene therapy.

Alleles↗
PubMed2000

Elevation of FVIII: C in venous thromboembolism is persistent and independent of the acute phase response.

Recent literature has suggested a role for elevated FVIII:C in venous thromboembolic disease (VTED). However since FVIII:C is known to rise in response to an acute phase reaction, it is difficult to determine whether the increased FVIII:C precedes the thrombosis or represents a secondary reactive phenomenon. In an attempt to address this question, we followed 35 patients with confirmed VTED, raised FVIII:C level (>1.5 iu/ml) and no other thrombotic tendency. Serial measurements of FVIII:C, vWF:Ag, C-reactive protein and fibrinogen were performed. We hypothesized that a persistent increase in FVIII:C in the absence of any other measures of ongoing acute phase response, would support the idea that elevation of FVIII:C is a constitutional phenomenon. Of this initial group, 94% continued to have an elevated FVIII:C level throughout the period of follow up (median 8 months; range 3 to 39 months), with no significant difference between the FVIII:C levels determined at first estimation and those obtained during follow up (p = 0.58). Conversely, only 18% had evidence of an acute phase reaction when first assessed, and nonparametric ranking analysis demonstrated no correlation between FVIII:C and either C-reactive protein or fibrinogen (p = 0.315 and 0.425 respectively).We conclude that increased FVIII:C levels following VTED are persistent, independent of the acute phase reaction, and thus may represent a constitutional risk factor for VTED.

Acute-Phase Reaction↗