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Biomedical subjects

G Snell

Publications and source records attributed to G Snell.

At least 19 recordsLinked to original sources
PubMed2006

Spectroscopic analysis of small organic molecules: a comprehensive near-edge x-ray-absorption fine-structure study of C6-ring-containing molecules.

We report high-resolution C 1s near-edge x-ray-absorption fine-structure (NEXAFS) spectra of the C6-ring-containing molecules benzene (C6H6), 1,3- and 1,4-cyclohexadiene (C6H8), cyclohexene (C6H10), cyclohexane (C6H12), styrene (C8H8), and ethylbenzene (C8H10) which allow us to examine the gradual development of delocalization of the corresponding pi electron systems. Due to the high experimental resolution, vibrational progressions can be partly resolved in the spectra. The experimental spectra are compared with theoretical NEXAFS spectra obtained from density-functional theory calculations where electronic final-state relaxation is accounted for. The comparison yields very good agreement between theoretical spectra and experimental results. In all cases, the spectra can be described by excitations to pi*- and sigma*-type final-state orbitals with valence character, while final-state orbitals of Rydberg character make only minor contributions. The lowest C 1s-->1pi* excitation energy is found to agree in the (experimental and theoretical) spectra of all molecules except for 1,3-cyclohexadiene (C6H8) where an energy smaller by about 0.6 eV is obtained. The theoretical analysis can explain this result by different binding properties of this molecule compared to the others.

Journal Article↗
PubMed2005

133Xenon ventilation scintigraphy applied to bronchoscopic lung volume reduction techniques for emphysema: relevance of interlobar collaterals.

BACKGROUND: 133Xenon ventilation scintigraphy and (99m)Tc-MAA perfusion scintigraphy can be used to assess dynamic ventilation patterns in patients with severe emphysema. AIM: To describe the scintigraphic features of attempted bronchoscopic lung volume reduction (BLVR), exploring mechanisms that might explain the unexpected lack of postoperative atelectasis. METHODS: Five patients with heterogenous severe upper lobe emphysema were evaluated with 133Xenon ventilation and (99m)Tc-MAA perfusion scintigraphy, chest radiography, bronchoscopy and high resolution computed tomography before and up to 1 month after endoscopic placement of bronchial prostheses (BLVR). Ex vivo assessment of the lungs of two further patients with severe upper lobe emphysema was performed. RESULTS: No significant subsegmental or lobar collapse was evident on post-procedure chest radiography or high resolution computed tomography, despite bronchoscopic confirmation of adequate position and functioning of prostheses. 133Xenon ventilation scintigraphy confirms significantly decreased upper lobe wash-in (P < 0.023), unchanged lower lobe wash-in and significantly increased lower lobe wash-out rates (P < 0.005) after BLVR. Significant redistribution of perfusion to the lower lobes occurred after BLVR (P < 0.025). Ex vivo experiments on explanted emphysematous lungs demonstrated that these findings could best be explained by collateral interlobar ventilation, which was calculated in one specimen to be as high as 15% of total lower lobe ventilation. Peri-valvular leak is a much less likely possibility. CONCLUSION: 133Xenon ventilation scintigraphy indicated the presence of significant interlobar collateral ventilation in patients with severe emphysema that may have major relevance to these novel alternative techniques to lung volume reduction surgery. 133Xenon scintigraphy can be used in the evaluation of severe emphysema before and after novel therapeutic interventions.

Bronchoscopy↗
PubMed2004

Probing the molecular environment using spin-resolved photoelectron spectroscopy.

Angle- and spin-resolved photoelectron spectroscopy with linearly and circularly polarized synchrotron radiation were used to study the electronic structure of model triatomic molecules, hydrogen sulfide, and carbonyl sulfide. The spin-polarization measurements of the molecular field split components of the S 2p photolines revealed a strong effect of the different molecular environments. The validity of simple atomic models to explain the results is discussed.

Journal Article↗
PubMed2002

Experimental evidence of a dynamic Jahn-Teller effect in C60(+).

Detailed analysis of the highest occupied molecular orbital band shape in the photoelectron spectrum of gaseous C60 reveals a dynamic Jahn-Teller effect in the ground state of C60(+). The direct observation of three tunneling states asserts a D(3d) geometry for the isolated cation, originating from a strong vibronic coupling. These results show that the ionic motion plays an important role in the electron-phonon interaction.

Journal Article↗
PubMed2001

Dynamical relativistic effects in photoionization: spin-orbit-resolved angular distributions of xenon 4d photoelectrons near the Cooper minimum.

Two decades ago, it was predicted [Y. S. Kim et al., Phys. Rev. Lett. 46, 1326 (1981)] that relativistic effects should alter the dynamics of the photoionization process in the vicinity of Cooper minima. The present experimental and theoretical study of the angular distributions of Xe 4d(3/2) and 4d(5/2) photoelectrons demonstrates this effect for the first time. The results clearly imply that relativistic effects are likely to be important for intermediate- Z atoms at most energies.

Journal Article↗
PubMed2001

Iron overload and nitric oxide-derived oxidative stress following lung transplantation.

BACKGROUND: Reactive oxygen species (ROS) may contribute to airway injury and the development of the bronchiolitis obliterans syndrome (BOS) following lung transplantation (LT). Chemically active iron released from ferritin stores and nitric oxide (NO)-derived radicals may add to the oxidative burden. METHODS: We determined the concentrations of ferritin and the aqueous NO derivative nitrite (NO2(-)) within bronchoalveolar lavage fluid (BALF) of 14 stable LT recipients (ST) and 7 subjects with BOS and 21 normal controls. We also assessed the relationship between BALF ferritin and hemosiderin-laden macrophages (HLMs) using a hemosiderin score (HS) and determined BALF albumin concentration as a marker of microvascular leakage. RESULTS: BALF ferritin concentrations and HSs were significantly elevated in LT recipients overall compared with normal controls (p < 0.05). BALF NO2(-) levels were elevated in BOS subjects and STs compared with normal controls (p = 0.002 and p = 0.09, respectively), but there was no difference between transplant groups. BALF albumin concentrations were elevated in BOS patients compared with normal controls (p = 0.02) and ST (p = 0.05), but there was no difference between STs and controls. There was a significant relationship between BALF ferritin concentration and HS in LT recipients overall (r(s) = 0.7, p < 0.001). In BOS subjects, but not ST, BALF ferritin was significantly related to BALF albumin (r(s) = 0.8, p = 0.05) and there was a weak relationship with NO2(-) concentration (r(s) = 0.6, p = 0.1). BALF NO2(-) was strongly related to BALF % neutrophils in BOS subjects (r(s) = 0.9, p < 0.01), but there was no such relationship in STs. CONCLUSIONS: Our findings suggest that the allograft could be subject to significant iron-generated oxidative stress, which may be exacerbated by NO and neutrophil-derived ROS, particularly in BOS. Microvascular leakage may be a feature of established chronic rejection, which potentiates the iron overload and contributes to further airway damage and remodeling.

Adult↗
PubMed2001

Bronchoalveolar lavage macrophage and lymphocyte phenotypes in lung transplant recipients.

Recent publications have demonstrated potentially pathologic changes in bronchoalveolar lavage (BAL) from clinically stable lung transplant recipients (SLTRs), but there are few available data on alveolar macrophages (AMs). We formulated the hypothesis that changes in BAL AM and lymphocyte phenotypes would be apparent even in SLTRs.A cross-sectional study using a standardized 3 x 60 ml BAL, investigating lymphocyte and AM phenotypes in 19 SLTRs, 5 subjects with bronchiolitis obliterans syndrome (BOS) and 18 normal control volunteers. BAL lymphocyte and AM markers were assessed using flow cytometry. We confirmed a significant elevation of neutrophils in all lung transplant recipients with a more marked elevation in the BOS subjects. Flow-cytometric analysis showed increased numbers of natural killer (NK; CD56/CD16-positive) cells, increased CD11b- and CD11c-positive CD3 lymphocytes, increased CD8-positive lymphocytes and increased HLA-DR expression in CD8 cells from the lung transplant recipients, when compared with normals (p <.005). In contrast, the expression of a number of AM surface markers, associated with a range of host defense functions against bacteria, fungi and viruses (CD11a, CD11b, CD11c, HLA-DR, CD14), was lower in both SLTRs and those with BOS (p <.05). These novel findings are consistent with complex lymphocyte and macrophage changes that may result from clinically silent infection, partially suppressed rejection, or both.

Adult↗
PubMed2000

Bronchoalveolar lavage cellular profiles in lung transplantation: the effect of inhaled corticosteroids.

UNLABELLED: Bronchiolitis Obliterans Syndrome (BOS) remains a major cause of long term morbidity and mortality in lung transplantation, and occurs despite significant immunosuppression. Airway inflammation is thought to precede the development of BOS. OBJECTIVES: To examine the effect of inhaled corticosteroids on airway inflammation and the development of BOS in lung transplant recipients. METHODS: 30 patients were recruited and randomised in a double blind fashion to receive either 750 micrograms Fluticasone propionate (FP) twice daily or an identical appearing placebo for 3 months. BAL cell counts and differentials were performed at time 0 and after 3 months treatment. Lung function was assessed at each time point using spirometry. RESULTS: 24 patients were felt to be stable and free from infection at both time points and thus included in the analysis. There was a significant reduction in total cell count in BAL fluid after treatment with 3 months FP compared to 3 months placebo, however no change in cell differentials nor lung function was found. DISCUSSION: Despite a reduction in total cell numbers in BAL fluid, lung function was not altered over the 3 months of treatment. It may be that longer treatment is required to see an effect.

Administration, Inhalation↗
PubMed1995

Akv murine leukemia virus enhances bone tumorigenesis in hMT-c-fos-LTR transgenic mice.

hMt-c-fos-LTR transgenic mice (U. Rüther, D. Komitowski, F. R. Schubert, and E. F. Wagner. Oncogene 4, 861-865, 1989) developed bone sarcomas in 20% (3/15) of females at 448 +/- 25 days and in 8% (1/12) of males at 523 days. After infection of newborns with Akv, an infectious retrovirus derived from the ecotropic provirus of the AKR mouse, 69% (20/28) of female animals and 83% (24/29) of males developed malignant fibrous-osseous tumors. The tumors in infected transgenics developed with higher frequency and a 200-days shorter mean tumor latency period. The hMt-c-fos-LTR transgene was expressed in all the fibrous-osseous tumors. They also showed newly integrated Akv proviruses, but in most tumors Akv was detected and expressed in only a small number of the tumor cells. Wild-type C3H mice infected with Akv developed benign osteomas with an incidence of 33% and a latency period of 474 days. The data indicate that Akv exerts distinct pathogenic effects on the skeleton. In hMt-c-fos-LTR transgenic mice, predisposed to bone sarcomagenesis, Akv acts synergistically with the fos transgene, resulting in the development of fibrous-osseous tumors.

AKR murine leukemia virus↗
PubMed1995

Multi-organ donor transmission of hepatitis C virus to five solid organ transplant recipients and lack of transmission to corneal transplant recipients.

BACKGROUND: A multi-organ donor seronegative for hepatitis C virus (HCV) by 1st generation enzyme immunoassay (EIA) supplied 5 solid organs and 2 corneas to 7 recipients. This donor was retrospectively shown to be 2nd generation HCV EIA-positive and polymerase chain reaction (PCR)-positive. All 5 solid organ recipients but none of the corneal recipients developed HCV infection. OBJECTIVES: To demonstrate the discordance between serological and PCR-based HCV detection in solid organ transplant recipients and the lack of transmission of HCV to the two corneal transplant recipients. STUDY DESIGN: All 5 solid organ recipients were retrospectively shown to be HCV PCR-negative and -seronegative pre-transplant and HCV PCR-positive post-transplant. Serial serum samples on 3 recipients were evaluated by 2nd generation EIA, a prototypic structural and non-structural dual bead assay (EIA-SA, Abbott), the Chiron Recombinant Immunoblot Assay, 2nd generation (RIBA-2), and the Chiron RIBA HCV Test System Strip Immunoblot Assay 3.0 (RIBA-3, Chiron). RESULTS: The dual bead EIA-SA and RIBA-3 were able to detect HCV seroconversion approximately 6 months earlier than the 2nd generation EIA in 2 recipients, and in 1 recipient only PCR detected infection within the first 10 months. There was no evidence of HCV transmission to the corneal recipients. CONCLUSIONS: Although third generation assays such as the RIBA-3 and EIA-SA narrowed the window of HCV seronegativity in transplant recipients compared with the 2nd generation EIA, PCR was the most sensitive method of detecting acute HCV infection. Despite transmission of HCV to all of the solid organ recipients HCV was not transmitted to the corneal transplant recipients.

Journal Article↗
PubMed1994

[Murine leukemia virus Akv promotes bone tumor development in fos-transgenic mice].

Newborn hMT-fos-LTR transgenic C3H mice and their non-transgenic siblings were infected with Akv, derived from the ecotropic provirus of the AKR mouse. Bone sarcomas in non-infected transgenics were observed in 20% (3/15) of females at 448 +/- 25 days and in 8% (1/12) of males at 523 days. Akv-infected transgenics developed bone tumors with higher frequency and at younger age: Females in 69% (20/28) at 268 +/- 122 days, males in 83% (24/29) at 279 +/- 109 days. In the majority of the bone tumors of Akv-infected transgenics (70% in females, 59% in males) cellular atypia was lacking and the histological pattern resembled human parosteal osteosarcoma. Only 50% (12/24) of bone tumors in Akv-infected transgenics revealed newly integrated virus sequences by Southern analysis. PCR analysis detected Akv sequences in DNAs of all tumors. Obviously, the insertion of Akv in a few cells induced the considerably accelerated bone tumor growth.

Animals↗