Search PubMed⌕ Search

Biomedical subjects

C M Evans

Publications and source records attributed to C M Evans.

At least 19 recordsLinked to original sources
PubMed2005

Energy of the quasi-free electron in supercritical krypton near the critical point.

Field ionization measurements of high-n CH(3)I and C(2)H(5)I Rydberg states doped into krypton are presented as a function of krypton number density along the critical isotherm. These data exhibit a decrease in the krypton-induced shift of the dopant ionization energy near the critical point. This change in shift is modeled to within +/-0.2% of experiment using a theory that accounts for the polarization of krypton by the dopant ion, the polarization of krypton by the quasi-free electron that arises from field ionization of the dopant, and the zero point kinetic energy of the free electron. The overall decrease in the shift of the dopant ionization energy near the critical point of krypton, which is a factor of 2 larger than that observed in argon, is dominated by the increase in the zero point kinetic energy of the quasi-free electron.

Journal Article↗
PubMed2002

Evaluation of extracorporeal shock wave therapy in Peyronie's disease.

OBJECTIVES: To evaluate the results of extracorporeal shock wave therapy (ESWT) in patients with Peyronie's disease. METHODS: This study included 42 patients (mean age 55.4 years, range 32 to 72, SD 9.92) with Peyronie's disease. The mean duration of disease was 16.5 months (range 3 to 60, SD 13.31). Before treatment, the degree of angulation was assessed artificially by injection of 10 to 20 microg alprostadil, and Polaroid photographs were taken. Patients were also questioned about pain on erection, whether sexual intercourse was possible, and the quality of erections. All were initially treated with three sessions of ESWT (3000 shock waves). After three sessions, patients who believed that improvement had resulted or who wanted to undergo additional treatment went on to have further sessions. The mean duration of follow-up was 5.9 months (range 2 to 18, SD 4.4), after which the results were analyzed. RESULTS: Those who believed that improvement in angulation had resulted were asked to provide Polaroid photographs to assess the improvement objectively. Six (14%) said that they had excellent results, 21 (50%) had significant improvement, 7 (17%) had slight improvement, and 8 (19%) had no change. Of the 25 who had pain on erection before treatment, 21 (84%) reported complete or near complete relief after treatment. Five patients said that the quality of the erections had improved after treatment. Eight patients complained of mild and one of severe pain during or immediately after treatment; 2 of these 9 patients had both pain and bruising. CONCLUSIONS: The initial results with ESWT are promising, with minimal complications. The long-term results need to be evaluated.

Adult↗
PubMed2001

Pre-reactive complexes in mixtures of water vapour with halogens: characterisation of H2O...ClF and H2O...F2 by a combination of rotational spectroscopy and ab initio calculations.

Complexes H2O...ClF and H2O...F2 were detected by means of their ground-state rotational spectra in mixtures of water vapour with chlorine monofluoride and difluorine, respectively. A fast-mixing nozzle was used in conjunction with a pulsed-jet, Fourier-transform microwave spectrometer to preclude the vigorous chemical reaction that these dihalogen species undergo with water. The ground-state spectra of seven isotopomers (H2 16O...35ClF, H2 16O...ClF, H2 18O...35ClF, D2 16O... 35ClF, D2 16O...37ClF, HDO...35ClF and HDO...37ClF) of the ClF complex and five isotopomers (H2O...F2, H2 18O...F2, D2O...F2, D2 18O...Fi and HDO...F2) of the F2 complex were analysed to yield rotational constants, quartic centrifugal distortion constants and nuclear hyperfine coupling constants. These spectroscopic constants were interpreted with the aid of simple models of the complexes to give effective geometries and intermolecular stretching force constants. Isotopic substitution showed that in each complex the H2O molecule acts as the electron donor and either CIF or F2 acts as the electron acceptor, with nuclei in the order H2O...ClF or H2O...F2. For H2O...ClF, the angle phi between the bisector of the HOH angle and the O...Cl internuclear line has the value 58.9(16)degrees, while the distance r(O...Cl)= 2.6081(23) A. The corresponding quantities for H2O...F2 are phi = 48.5(21)degrees and r(O...Fi) = 2.7480(27) A, where Fi indicates the inner F atom. The potential energy V(phi) as a function of the angle phi was obtained from ab initio calculations at the aug-cc-pVDZ/MP2 level of theory for each complex by carrying out geometry optimisations at fixed values of phi in the range +/-80degrees. The global minimum corresponded to a complex of Cs symmetry with a pyramidal configuration at O in each. The function V(phi) was of the double-minimum type in each case with equilibrium values phie = +/-55.8degrees and +/-40.5degrees for H2O...ClF and H2O...F2, respectively. The barrier at the planar C2v conformation was V0= 174cm(-1) for H2O...ClF and 7cm(-1) for H2O...F2. For the latter complex, the zero-point energy level lies above the top of the barrier.

Journal Article↗
PubMed2001

Effects of dexamethasone on antigen-induced airway eosinophilia and M(2) receptor dysfunction.

In antigen-challenged guinea pigs, airway hyperreactivity is due to recruitment of eosinophils to the airway nerves and dysfunction of M(2) muscarinic receptors. M(2) receptor dysfunction is caused by eosinophil major basic protein, which is an allosteric antagonist at the receptor. Because glucocorticoids inhibit airway hyperreactivity in humans and in animal models of asthma, we tested whether dexamethasone treatment (6 microg. kg(-)(1). d(-)(1) for 3 d, intraperitoneal) before antigen challenge prevents M(2) receptor dysfunction and airway hyperreactivity. Guinea pigs were sensitized to ovalbumin via intraperitoneal injections, and were challenged with ovalbumin via inhalation. Twenty-four hours later, hyperreactivity and M(2) receptor function were tested. Antigen-challenged animals were hyperreactive to vagal stimulation, and demonstrated loss of M(2) receptor function. Dexamethasone pretreatment prevented hyperreactivity and M(2) receptor dysfunction in antigen-challenged guinea pigs. Antigen challenge resulted in recruitment of eosinophils to the airways and to the airway nerves. Dexamethasone prevented recruitment of eosinophils to the airway nerves but did not affect total eosinophil influx into the airways. These results demonstrate that dexamethasone prevents antigen-induced hyperreactivity by protecting neuronal M(2) muscarinic receptors from antagonism by eosinophil major basic protein, and this protective mechanism appears to be by specifically inhibiting eosinophil recruitment to the airway nerves.

Analysis of Variance↗
PubMed2000

Substance P-induced airway hyperreactivity is mediated by neuronal M(2) receptor dysfunction.

Neuronal muscarinic (M(2)) receptors inhibit release of acetylcholine from the vagus nerves. Hyperreactivity in antigen-challenged guinea pigs is due to blockade of these M(2) autoreceptors by eosinophil major basic protein (MBP) increasing the release of acetylcholine. In vivo, substance P-induced hyperactivity is vagally mediated. Because substance P induces eosinophil degranulation, we tested whether substance P-induced hyperreactivity is mediated by release of MBP and neuronal M(2) receptor dysfunction. Pathogen-free guinea pigs were anesthetized and ventilated. Thirty minutes after intravenous administration of [Sar(9),Met(O(2))(11)]- substance P, guinea pigs were hyperreactive to vagal stimulation and M(2) receptors were dysfunctional. The depletion of inflammatory cells with cyclophosphamide or the administration of an MBP antibody or a neurokinin-1 (NK(1)) receptor antagonist (SR-140333) all prevented substance P-induced M(2) dysfunction and hyperreactivity. Intravenous heparin acutely reversed M(2) receptor dysfunction and hyperreactivity. Thus substance P releases MBP from eosinophils resident in the lungs by stimulating NK(1) receptors. Substance P-induced hyperreactivity is mediated by blockade of inhibitory neuronal M(2) receptors by MBP, resulting in increased release of acetylcholine.

Animals↗
PubMed1999

Antigen-induced hyperreactivity to histamine: role of the vagus nerves and eosinophils.

M2 muscarinic receptors limit acetylcholine release from the pulmonary parasympathetic nerves. M2 receptors are dysfunctional in antigen-challenged guinea pigs, causing increased vagally mediated bronchoconstriction. Dysfunction of these M2 receptors is due to eosinophil major basic protein, which is an antagonist for M2 receptors. Histamine-induced bronchoconstriction is composed of a vagal reflex in addition to its direct effect on airway smooth muscle. Because hyperreactivity to histamine is seen in antigen-challenged animals, we hypothesized that hyperreactivity to histamine may be due to increased vagally mediated bronchoconstriction caused by dysfunction of M2 receptors. In anesthetized, antigen-challenged guinea pigs, histamine-induced bronchoconstriction was greater than that in control guinea pigs. After vagotomy or atropine treatment, the response to histamine in antigen-challenged animals was the same as that in control animals. In antigen-challenged animals, blockade of eosinophil influx into the airways or neutralization of eosinophil major basic protein prevented the development of hyperreactivity to histamine. Thus hyperreactivity to histamine in antigen-challenged guinea pigs is vagally mediated and dependent on eosinophil major basic protein.

Animals↗
PubMed1997

Pretreatment with antibody to eosinophil major basic protein prevents hyperresponsiveness by protecting neuronal M2 muscarinic receptors in antigen-challenged guinea pigs.

In antigen-challenged guinea pigs there is recruitment of eosinophils into the lungs and to airway nerves, decreased function of inhibitory M2 muscarinic autoreceptors on parasympathetic nerves in the lungs, and airway hyperresponsiveness. A rabbit antibody to guinea pig eosinophil major basic protein was used to determine whether M2 muscarinic receptor dysfunction, and the subsequent hyperresponsiveness, are due to antagonism of the M2 receptor by eosinophil major basic protein. Guinea pigs were sensitized, challenged with ovalbumin and hyperresponsiveness, and M2 receptor function tested 24 h later with the muscarinic agonist pilocarpine. Antigen-challenged guinea pigs were hyperresponsive to electrical stimulation of the vagus nerves compared with controls. Likewise, loss of M2 receptor function was demonstrated since the agonist pilocarpine inhibited vagally-induced bronchoconstriction in control but not challenged animals. Pretreatment with rabbit antibody to guinea pig eosinophil major basic protein prevented hyperresponsiveness, and protected M2 receptor function in the antigen-challenged animals without inhibiting eosinophil accumulation in the lungs or around the nerves. Thus, hyperresponsiveness is a result of inhibition of neuronal M2 muscarinic receptor function by eosinophil major basic protein in antigen-challenged guinea pigs.

Acetylcholine↗
PubMed1996

Stingray hickey.

A large number of injuries from stingrays are reported each year in the United States. Usually these injuries are inflicted by the stingray's tail, after the resting stingray is stepped on. The tail has a stinger that can cause puncture wounds with envenomation. We report a case in which an injury from a stingray was due to its bite.

Adult↗
PubMed1993

Supporting future surgical innovation. Lung transplantation as a case study.

OBJECTIVE: Using lung transplantation as a case study, this article addressed the problem of supporting innovative clinical surgery in an era of increasing pressures for cost containment. SUMMARY BACKGROUND DATA: After sporadic attempts at lung transplantation during the 1960s and 1970s, its clinical development began in earnest during the early 1980s. As a result of a wide range of incremental advances, the results have improved significantly. The Health Care Financing Administration, however, has not yet issued a national policy covering lung transplants and has left the coverage decision to the discretion of its regional contractors. METHODS: The authors surveyed the major commercial insurers, the Blue Cross Blue Shield Association, and a sample of Medicare intermediaries to evaluate the coverage of lung transplantation. They also interviewed the National Heart, Lung, and Blood Institute and industrial firms about their support for clinical research. RESULTS: Government and industry funding were limited, and the development and assessment of lung transplants have been financed predominantly by academic institutions through cross-subsidization from patient care and teaching funds. The major private payers and Blue Cross Blue Shield decided to cover this procedure in the early 1990s. Coverage decisions by Medicare intermediaries, however, revealed considerable variability. Moreover, the absence of a specific diagnosis-related group for lung transplants had considerable consequences for institutions in all-payer states, in which payments appeared to be considerably lower than the mean costs of a transplant procedure (about $110,000). CONCLUSIONS: This analysis indicated that there was a growing disparity between the increasing demand for outcomes data about new procedures and the limited resources available for supporting the development and assessment of new operations. It this disparity is not addressed, the rate of surgical innovation may be jeopardized, and timely outcomes data may not be acquired. It was concluded that provisional coverage within a predetermined research protocol may be a promising mechanism to remedy this situation, providing timely assessment of new procedures before widespread application.

Centers for Medicare and Medicaid Services, U.S.↗
PubMed1992

Activation of lamina propria T cells induces crypt epithelial proliferation and goblet cell depletion in cultured human fetal colon.

An organ culture model has been used to study the effects of T cell activation in the human colon. Lamina propria T cells in explant cultures of human fetal colon (11 to 23 weeks gestation) were activated in situ using pokeweed mitogen or an anti-CD3 monoclonal antibody, and compared with unstimulated controls. After three days of culture, there was a two to four-fold increase in crypt epithelial cell proliferation in T cell stimulated explants of more than 15 weeks gestation, associated with a fall in crypt goblet cell numbers of up to 20-fold. By three days, the surface epithelium of stimulated explants appeared thin with loss of goblet cells, and by day 7, severe and extensive mucosal damage was observed by light and electron microscopy. These changes did not occur in control cultures and explants deficient in T cells (less than 16 weeks gestation), and were inhibited by cyclosporin A. These experiments indicate that the increase in epithelial cell proliferation and accompanying goblet cell depletion observed in colorectal crypts in chronic inflammatory bowel disease may be mediated by activated T cells.

Cell Division↗
PubMed1990

Surgery for Crohn's disease in childhood: influence of site of disease and operative procedure on outcome.

Factors influencing outcome after surgery have been studied in 67 children requiring bowel resection or diversion of the faecal stream for Crohn's disease. Patients were divided into four groups on the basis of disease location at time of surgery, and mean follow-up was 4.5 years. All three children with panenteric disease (group 1) have relapsed. Best results were observed in cases with disease confined to the small bowel (group 2) and ileocaecal region (group 3), in whom surgery was followed by sustained remission in six out of seven and 24 out of 30 patients respectively. In the 27 children with colitis (group 4), results were mixed. Six of the seven patients who had staged colonic resections with a primary anastomosis relapsed, as did three out of four patients given a loop ileostomy to divert the faecal flow; in contrast, 15 out of 16 children who had a subtotal colectomy with ileostomy as the primary procedure have remained well, with only minor problems involving the rectal stump. An acceleration in growth velocity was observed during the first year after operation in 89 per cent of 40 children studied. Outcome after surgery for Crohn's disease in childhood depends mainly on disease location, but is influenced by the type of primary operation performed. In addition to symptomatic relief the principal early benefit of surgery is improved growth.

Adolescent↗
PubMed1990

Screening impotence by home nocturnal tumescence self-monitoring.

Twenty subjects complaining of impotence were assessed using nocturnal penile tumescence (NPT), neurological, vascular and hormonal analysis. Subjects undertook NPT in both home and hospital environments: 10 hospital first and 10 home first. There were high levels of agreement between diagnosis using NPT in the two conditions and diagnosis from the physiological tests. There was a high correlation of frequency of erections between the home and hospital conditions, together with a high consecutive night reliability when using the monitor in the home condition (r = .94, p = .001).

Diagnosis, Differential↗
PubMed1990

Three hundred sixty-five days post-HMO.

Carolina Medical Care was conceived as a physician-owned HMO. Two-and-a-half years later, it was declared insolvent and shut down. As a founding member of the HMO, a third of its 15,000 patients were capitated to the Mecklenburg Medical Group. This case study examines the efforts to keep those patients following dissolution of the HMO.

Group Practice↗
PubMed1990

Nursing salaries: a new strategy.

Salary inconsistencies in the nursing department of the Mecklenburg Medical Group were becoming a significant problem. This case study explains how the group implemented a system to bring nurses' salaries in line with the rest of the community.

Efficiency↗