Search PubMed⌕ Search

Biomedical subjects

M Tolan

Publications and source records attributed to M Tolan.

At least 19 recordsLinked to original sources
PubMed2003

Observation of heterodyne mixing in surface x-ray photon correlation spectroscopy experiments.

We report measurements of propagating capillary waves on a liquid water surface at T=5 degrees C with x-ray photon correlation spectroscopy. The experiment has been performed under grazing incidence conditions with an incoming x-ray beam below the critical angle of total external reflection. In the q region investigated the measured intensity-intensity autocorrelation functions of the liquid water surface were found to be heterodyne signals, i.e., a combination of first- and second-order correlation functions g(1)(tau) and g(2)(tau).

Journal Article↗
PubMed2003

X-ray scattering from freestanding polymer films with geometrically curved surfaces.

We show that the x-ray surface scattering from a freestanding polymer film exhibits features that cannot be explained by the usual stochastic formalism for surfaces with random height fluctuations. Instead, a geometric description of the film morphology assuming two curved surfaces characterized by a radius of curvature and a lateral cutoff length successfully accounts for the phase difference between the Kiessig fringes of the nominal "specular" and "off-specular" components of the scattering. The formalism allows one to distinguish unambiguously between conformal and anticonformal curvature morphologies at long length scales.

Journal Article↗
PubMed2003

Chronic osteomyelitis mimicking sarcoma.

This report describes a rare case of chronic osteomyelitis in a 60 year old man mimicking a soft tissue sarcoma. Chronic osteomyelitis is an infrequent cause of a soft tissue mass and is usually diagnosed clinically by a combination of radiology and microbiology. Rarely, COM can mimic a primary bony neoplasm, but this is the first reported case where it mimicked a soft tissue sarcoma. The clinical, radiological, and histological appearances of this case will be discussed.

Chronic Disease↗
PubMed2001

X-ray reflectivity study on the surface and bulk glass transition of polystyrene.

The surfaces of polystyrene (PS) films decorated with gold nanoclusters were investigated by x-ray reflectivity measurements. The thicknesses of the films are much larger than the radii of gyration of the different PS samples. By annealing the films above the glass transition temperature T(g) an embedding process of the clusters into the polymer is detected which is accompanied by a substantial increase in the cluster layer thickness due to Brownian motion. These processes start at a sufficiently low viscosity and may be regarded as a probe of the glass transition in the near surface region of the PS films. Simultaneously the thermal expansion of the entire film and hence its approximate bulk behavior were monitored. Two samples of different molecular weight do not show a significant difference between the surface and bulk T(g) values.

Journal Article↗
PubMed1998

Life-supporting pig-to-primate renal xenotransplantation using genetically modified donors.

BACKGROUND: In order to circumvent the complement-mediated hyperacute rejection of discordant xenografts, a colony of pigs transgenic for the human regulator of complement activity, human decay-accelerating factor (hDAF), has been produced. METHODS: Seven kidneys from hDAF transgenic pigs and six kidneys from nontransgenic control pigs were transplanted into cynomolgus monkeys; both native kidneys were removed during the same operation. The recipient animals were immunosuppressed with cyclosporine, steroids, and cyclophosphamide. RESULTS: In the transgenic group, the median survival time was 13 days (range, 6-35 days); the median survival time in the control group was 6.5 days (range, 0.3-30 days). There were no cases of hyperacute rejection in the transgenic group, and the two longest-surviving kidneys in this group showed no evidence of rejection on histological examination. In contrast, all control kidneys underwent antibody-mediated rejection, one demonstrating hyperacute rejection and the others acute vascular rejection. CONCLUSION: This study demonstrates that (i) a kidney from an hDAF transgenic pig can support the life of a primate for up to 35 days (and also shows the basic physiological compatibility between the pig and nonhuman primate); (ii) nontransgenic kidneys are not routinely hyperacutely rejected; and (iii) the presence of hDAF on the kidney confers some protection against acute vascular rejection. Improved immunosuppression and immunological monitoring may enable extended survival.

Animals↗
PubMed1998

Life-supporting pig-to-baboon heart xenotransplantation.

BACKGROUND: The aim of this study was to investigate the effect of the expression of human decay-accelerating factor in transgenic pigs on hyperacute rejection in a pig-to-baboon heterotopic heart transplantation model and to assess the ability of such transgenic pig hearts in supporting the life of a primate when transplanted orthotopically. METHODS: Hearts from pigs transgenic for human decay-accelerating factor were transplanted heterotopically (n = 3) and orthotopically (n = 5) into the baboon. All animals received cyclosporine, steroids, and cyclophosphamide. Blood was sampled regularly for total antipig antibody titers, trough cyclosporine levels, full blood count, electrolytes, and creatinine. Rejection of the heterotopic hearts was defined as the absence of palpable cardiac pulsation. Explanted hearts were examined histologically with hematoxylin and eosin and with immunochemistry for complement components C3, C4, C9, and immunoglobulin M. RESULTS: None of the hearts were hyperacutely rejected. In the heterotopic group one heart underwent acute vascular rejection on day 13, and the remaining two recipients with beating xenografts were killed on days 2 and 21. In the orthotopic group, one recipient with a life-supporting xenograft was killed on day 9 because of poor general condition. Histologic examination demonstrated no evidence of rejection. Two xenografts stopped beating on day 5, and histologic study showed acute vascular rejection in both. There were also two graft failures for technical reasons in this group. CONCLUSIONS: Hyperacute rejection is abrogated in pig-to-baboon heart xenotransplantation with the expression of the human decay-accelerating factor transgene. The human decay-accelerating factor transgenic pig heart is able to support primate life for a prolonged period.

Animals↗
PubMed1996

Homograft replacement of the mitral valve. Graft selection, technique of implantation, and results in forty-three patients.

UNLABELLED: Because of experience gained in reconstructive mitral valve surgery, we have reevaluated the implantation of cryopreserved homografts in the mitral position. Forty-three patients, aged 11 to 69 years (mean 34 years), underwent mitral valve replacement with cryopreserved mitral homografts. The indications for the procedure were acute endocarditis (n = 14), rheumatic stenosis (n = 26), systemic lupus endocarditis (n = 2), and marasmic endocarditis (n = 1). All homografts were obtained from hearts explanted in the course of transplantation and were cryopreserved at -160 degrees C in 10% dimethyl sulfoxide solution without antibiotics. Appropriate sizing was based on morphologic study of the homografts and preoperative echocardiographic assessment of the recipient valve. In 82 homografts analyzed, the height of the anterior leaflet was 25 +/- 3 mm and the distance from the anulus to the apex of the anterior papillary muscle was 21 +/- 3 mm. The morphologic features of the papillary muscles were classified according to four types of increasing complexity. Nine valves with complex (type IV) papillary muscle abnormalities were discarded. Echocardiographic measurements of the valve were matched with those of the homograft identification cards and a slightly larger homograft was selected (measurements + 3 mm). Partial homograft replacement was done in case of a localized lesion (abscess or calcification) (n = 21). Total homograft replacement was undertaken in the presence of diffuse lesions (n = 22). Two hospital deaths occurred as a result of poor cardiac output. One patient required reoperation on the tenth postoperative day after a dehiscence on the valvular suture line. After a mean follow-up of 14 months, there has been one late death caused by a bronchial neoplasm and one reoperation for residual stenosis (partial replacement). The remaining patients were in either New York Heart Association class I (n = 25) or II (n = 13). Thirty-three patients were in sinus rhythm. Follow-up echocardiography has revealed no mitral regurgitation (n = 20), minimal mitral regurgitation (n = 13), and mild mitral regurgitation (n = 5). Surface valve area has been calculated at 2.5 +/- 0.4 cm2 in partial homograft reconstruction and 2.7 +/- 0.3 cm2 in total homograft replacement, with a transvalvular gradient of 3 +/- 4 mm Hg. CONCLUSION: In a selected group of patients, the use of mitral homografts significantly extended the present limitations of reparative surgery of the mitral valve.

Adolescent↗
PubMed1995

Homograft replacement of fungal endocarditic pulmonary valve.

Right-sided infective endocarditis is uncommon but is increasingly seen as a reflection of the prevalence of drug abuse, chronic intravenous catheters and associated congenital malformations. Isolated pulmonary valve endocarditis has rarely been reported and there has been only one previous report of isolated pulmonary valve fungal endocarditis. This resolved with antimicrobials. We describe a case of isolated mycotic pulmonary valve endocarditis resistant to existing anti-fungal chemotherapy, which necessitated pulmonary valve resection and replacement with a homograft.

Adult↗
PubMed1995

Clinical experience with a collagen impregnated woven Dacron graft.

Vascular grafts continue to evolve. Recent developments have been aimed at decreasing porosity, increasing strength of prosthesis, increasing ease of handling and suturing and optimising flow characteristics. This study describes results with a recently developed collagen impregnated polyester prosthesis Hemashield Woven Double Velour, which does not require pre-clotting. Between January 1988 and December, 1991 such prostheses were used in 90 patients at Papworth Hospital. Fifty-eight, were used to replace the ascending aorta, 10 for the arch of the aorta and 28 for the descending aorta seven of whom were for coarctation and four for traumatic transections. In 60 cases the underlying disease was a dissected or ruptured aorta requiring emergency operation. There were 66 survivors with X-ray and CT follow-up of 6-52 months. Median blood loss was 630 ml range 380-1800 ml. There was no leakage from any of the grafts during surgery despite full perioperative heparinisation. For emergency/elective operations (N = 60/30) early mortality was 25%/10% (15/3) and late mortality 5%/6.6% (3/2). Of 15 patients who had interposition grafts for Type A dissection CT scans at 5-47 months showed one with chronic dissection proximal to the repair and 11 with persistent distal dissection. There was no evidence of late bleeding, seroma impaired healing or thickened neointima formation. It is concluded that there are no clinical disadvantages associated with collagen impregnation to set against the notable convenience of initial impermeability.

Adult↗
PubMed1995

Partial mitral homograft: a new technique for mitral valve repair.

Partial mitral homograft was used in 22 patients with localized lesions contraindicating a conventional valve repair. The etiologies of valve disease were: calcified rheumatic stenosis (n=14) and acute bacterial endocarditis (n=8). One patient died three months after surgery from cancer. Another patient required reoperation for residual stenosis 14 months postoperatively. All other patients had an excellent functional result with 19 patients in sinus rhythm. In this series, partial homograft replacement of the mitral valve significantly extended the possibilities of reconstructive surgery.

Adolescent↗
PubMed1993

Prophylactic digitalization fails to control dysrhythmia in thoracic esophageal operations.

A prospective, controlled, randomized study of 80 patients undergoing esophageal operations was undertaken, in which one group of patients was given digoxin and the other was not. The incidence of cardiac dysrhythmia was compared in each group. Twenty-six patients underwent operation for benign disease. Equal numbers were digitalized or not and no dysrhythmias occurred. Fifty-four patients underwent operation for malignant disease. Of 26 in the group digitalized, 12 suffered dysrhythmia (46%). Of 28 not digitalized, 9 suffered dysrhythmia (32%). Overall, 39% of patients with malignant disease suffered a dysrhythmia compared with none with benign disease (p < 0.002 by chi 2).

Aged↗
PubMed1993

Cardiac dysrhythmia in total thoracic oesophagectomy. A prospective study.

A prospective controlled randomized clinical study of 50 patients undergoing total thoracic oesophagectomy by one surgical team is described, in which one group of patients was given prophylactic digoxin and the other was not. The incidence of cardiac dysrhythmia in each group was compared. Fourteen (56%) of 25 patients digitalized, compared to 16 (64%) of 25 patients not digitalized, suffered cardiac dysrhythmia, with a total incidence of 30 patients (60%). The first onset of dysrhythmia occurred within 48 h in 89% of the patients who suffered this complication. These results indicate a high incidence of cardiac dysrhythmia in patients undergoing this operative procedure, which is not significantly reduced by prophylactic digitalization and which is likely to occur within 2 days of surgery.

Aged↗