Robust unfolding of MeV x-ray spectra from filter stack spectrometer data.

We present an inversion method capable of robustly unfolding MeV x-ray spectra from filter stack spectrometer (FSS) data without requiring an a priori specification of a spectral shape or arbitrary termination of the algorithm. Our inversion method is based upon the perturbative minimization (PM) algorithm, which has previously been shown to be capable of unfolding x-ray transmission data, albeit for a limited regime in which the x-ray mass attenuation coefficient of the filter material increases monotonically with x-ray energy. Our inversion method improves upon the PM algorithm through regular smoothing of the candidate spectrum and by adding stochasticity to the search. With these additions, the inversion method does not require a physics model for an initial guess, fitting, or user-selected termination of the search. Instead, the only assumption made by the inversion method is that the x-ray spectrum should be near a smooth curve. Testing with synthetic data shows that the inversion method can successfully recover the primary large-scale features of MeV x-ray spectra, including the number of x-rays in energy bins of several-MeV widths to within 10%. Fine-scale features, however, are more difficult to recover accurately. Examples of unfolding experimental FSS data obtained at the Texas Petawatt Laser Facility and the OMEGA EP laser facility are also presented.

Frequency-dependent shear properties of annulus fibrosus and nucleus pulposus by magnetic resonance elastography.

Aging and degeneration are associated with changes in mechanical properties in the intervertebral disc, generating interest in the establishment of mechanical properties as early biomarkers for the degenerative cascade. Magnetic resonance elastography (MRE) of the intervertebral disc is usually limited to the nucleus pulposus, as the annulus fibrosus is stiffer and less hydrated. The objective of this work was to adapt high-frequency needle MRE to the characterization of the shear modulus of both the nucleus pulposus and annulus fibrosus. Bovine intervertebral discs were removed from fresh oxtails and characterized by needle MRE. The needle was inserted in the center of the disc and vibrations were generated by an amplified piezoelectric actuator. MRE acquisitions were performed on a 4.7-T small-animal MR scanner using a spin echo sequence with sinusoidal motion encoding gradients. Acquisitions were repeated over a frequency range of 1000-1800 Hz. The local frequency estimation inversion algorithm was used to compute the shear modulus. Stiffness maps allowed the visualization of the soft nucleus pulposus surrounded by the stiffer annulus fibrosus surrounded by the homogeneous gel. A significant difference in shear modulus between the nucleus pulposus and annulus fibrosus, and an increase in the shear modulus with excitation frequency, were observed, in agreement with the literature. This study demonstrates that global characterization of both the nucleus pulposus and annulus fibrosus of the intervertebral disc is possible with needle MRE using a preclinical magnetic resonance imaging (MRI) scanner. MRE can be a powerful method for the mapping of the complex properties of the intervertebral disc. The developed method could be adapted for in situ use by preserving adjacent vertebrae and puncturing the side of the intervertebral disc, thereby allowing an assessment of the contribution of osmotic pressure to the mechanical behavior of the intervertebral disc.

Measurement of anisotropic mechanical properties in porcine brain white matter ex vivo using magnetic resonance elastography.

The mechanical properties of brain tissue, particularly those of white matter (WM), need to be characterized accurately for use in finite element (FE) models of brain biomechanics and traumatic brain injury (TBI). Magnetic resonance elastography (MRE) is a powerful tool for non-invasive estimation of the mechanical properties of soft tissues. While several studies involving direct mechanical tests of brain tissue have shown mechanical anisotropy, most MRE studies of brain tissue assume an isotropic model. In this study, an incompressible transversely isotropic (TI) material model parameterized by minimum shear modulus (µ2), shear anisotropy parameter (ϕ), and tensile anisotropy parameter (ζ) is applied to analyze MRE measurements of ex vivo porcine white matter (WM) brain tissue. To characterize shear anisotropy, "slow" (pure transverse) shear waves were propagated at 100, 200 and 300Hz through sections of ex vivo brain tissue including both WM and gray matter (GM). Shear waves were found to propagate with elliptical fronts, consistent with TI material behavior. Shear wave fields were also analyzed within regions of interest (ROI) to find local shear wavelengths parallel and perpendicular to fiber orientation. FE simulations of a TI material with a range of plausible shear modulus (µ2) and shear anisotropy parameters (ϕ) were run and the results were analyzed in the same fashion as the experimental case. Parameters of the FE simulations which most closely matched each experiment were taken to represent the mechanical properties of that particular sample. Using this approach, WM in the ex vivo porcine brain was found to be mildly anisotropic in shear with estimates of minimum shear modulus (actuation frequencies listed in parenthesis): µ2= 1.04 ± 0.12 kPa (at 100Hz), µ2= 1.94 ± 0.29 kPa (at 200Hz), and µ2= 2.88 ± 0.34 kPa (at 300Hz) and corresponding shear anisotropy factors of ϕ= 0.27 ± 0.09 (at 100Hz), ϕ= 0.29 ± 0.14 (at 200Hz) and ϕ= 0.34 ± 0.13 (at 300Hz). Future MRE studies will focus on tensile anisotropy, which will require both slow and fast shear waves for accurate estimation.

Magnetic resonance elastography of slow and fast shear waves illuminates differences in shear and tensile moduli in anisotropic tissue.

Mechanical anisotropy is an important property of fibrous tissues; for example, the anisotropic mechanical properties of brain white matter may play a key role in the mechanics of traumatic brain injury (TBI). The simplest anisotropic material model for small deformations of soft tissue is a nearly incompressible, transversely isotropic (ITI) material characterized by three parameters: minimum shear modulus (µ), shear anisotropy (ϕ=µ1µ-1) and tensile anisotropy (ζ=E1E2-1). These parameters can be determined using magnetic resonance elastography (MRE) to visualize shear waves, if the angle between the shear-wave propagation direction and fiber direction is known. Most MRE studies assume isotropic material models with a single shear (µ) or tensile (E) modulus. In this study, two types of shear waves, "fast" and "slow", were analyzed for a given propagation direction to estimate anisotropic parameters µ, ϕ, and ζ in two fibrous soft materials: turkey breast ex vivo and aligned fibrin gels. As expected, the speed of slow shear waves depended on the angle between fiber direction and propagation direction. Fast shear waves were observed when the deformations due to wave motion induced stretch in the fiber direction. Finally, MRE estimates of anisotropic mechanical properties in turkey breast were compared to estimates from direct mechanical tests.

Americans' health priorities: curing cancer and controlling costs.

In this paper we provide a comprehensive examination of Americans' priorities within both health and health care. We find that Americans do have a clear set of priorities in each of these areas. Americans rated cancer, human immunodeficiency virus (HIV)/acquired immunodeficiency syndrome (AIDS), and heart disease, and medical research to address these conditions, as top priorities among eighty health problems. However, they did not rank many leading causes of death very high as serious problems. On the issue of health care, problems of costs, prescription drugs, and the uninsured top the list. Americans are very concerned about emerging international infectious diseases that they believe threaten their health.

A microdilution plating method for population analysis of antibiotic-resistant staphylococci.

The microdilution plating method, using colony-forming units (CFU)/ml determinations from 10-microl droplets, was compared with the standard plate count in population analyses of methicillin-resistant and glycopeptide-intermediate Staphylococcus aureus (MRSA and GISA) strains. Efficiency of plating plots yielded similar population resistance profiles for both methods with MRSA class 1-4 strains, laboratory-selected GISA strains of varying susceptibilities, two clinical GISA strains, as well as susceptible strains. A single heterogeneous MRSA, plated by both methods in 41 trials with and without 50 microg/ml oxacillin present, demonstrated no significant difference between the results of the two methods of colony counting (p > 0.05, and r = 0.67). Standard plating and microdilution plating produced mean resistant subpopulation determinations of one cell in 1.19 x 10(4) and 1.36 x 10(4), respectively. Population analyses carried out by microdilution plating require one-fourth or fewer of the plates used for standard plating, and both plating and colony counting required less time to perform.

Endoscopic stapled diverticulotomy: treatment of choice for Zenker's diverticulum.

OBJECTIVE: To evaluate the efficacy and safety of endoscopic stapled diverticulotomy in the treatment of patients with Zenker's diverticulum. STUDY DESIGN: Cohort study. METHODS: Fourteen elderly patients (11 men and 3 women) with Zenker's diverticulum were evaluated in a community hospital setting from July 1996 to November 1999. Before surgery patients had significant dysphagia, regurgitation, cough, or aspiration pneumonia. The common septum between the diverticulum and cervical esophagus was visualized with a Weerda diverticuloscope. While using videoendoscopic monitoring, the septum was divided and the edges simultaneously sealed with a linear endoscopic stapler. Average operative time was 31 minutes. RESULTS: The operation was successfully performed in 11 of 14 patients. In the three unsuccessful cases, one patient's pouch was too small to staple and the other two patients had a septum that was difficult to visualize with the diverticuloscope. There was no significant postoperative morbidity or mortality. Patients started a liquid diet on the first postoperative day and resumed a soft diet a week later. They were usually discharged on the first postoperative day. Most patients reported significant improvement with resolution of dysphagia and regurgitation. CONCLUSIONS: Compared with the traditional open technique, the endoscopic stapled diverticulotomy technique is safe, quick, and effective and requires a shorter length of stay in the hospital. Therefore it has become our treatment of choice for elderly, high-risk patients with a large (>2 cm) hypopharyngeal (Zenker's) diverticulum.

Characterization of passage-selected vancomycin-resistant Staphylococcus aureus strains of diverse parental backgrounds.

A series of 12 Staphylococcus aureus strains of various genetic backgrounds, methicillin resistance levels, and autolytic activities were subjected to selection for the glycopeptide-intermediate S. aureus (GISA) susceptibility phenotype on increasing concentrations of vancomycin. Six strains acquired the phenotype rapidly, two did so slowly, and four failed to do so. The vancomycin MICs for the GISA strains ranged from 4 to 16 microg/ml, were stable to 20 nonselective passages, and expressed resistance homogeneously. Neither ease of acquisition of the GISA phenotype nor the MIC attained correlated with methicillin resistance hetero- versus homogeneity or autolytic deficiency or sufficiency. Oxacillin MICs were generally unchanged between parent and GISA strains, although the mec members of both isogenic methicillin-susceptible and methicillin-resistant pairs acquired the GISA phenotype more rapidly and to higher MICs than did their susceptible counterparts. Transmission electron microscopy revealed that the GISA strains appeared normal in the absence of vancomycin but had thickened and diffuse cell walls when grown with vancomycin at one-half the MIC. Common features among GISAs were reduced doubling times, decreased lysostaphin susceptibilities, and reduced whole-cell and zymographic autolytic activities in the absence of vancomycin. This, with surface hydrophobicity differences, indicated that even in the absence of vancomycin the GISA cell walls differed from those of the parents. Autolytic activities were further reduced by the inclusion of vancomycin in whole-cell and zymographic studies. The six least vancomycin-susceptible GISA strains exhibited an increased capacity to remove vancomycin from the medium versus their parent lines. This study suggests that while some elements of the GISA phenotype are strain specific, many are common to the phenotype although their expression is influenced by genetic background. GISA strains with similar glycopeptide MICs may express individual components of the phenotype to different extents.

[Effect of the fibrinous sorbent Akvalen on survival and spontaneous tumorigenesis in mice]. / Vliianie voloknistogo sorbenta Akvalen na prodolzhitel'nost' zhizni i vozniknovenie spontannykh opukholei u myshei.

SHP female mice were fed 100 mg/kg carbonic fibrilous sorbent Akvalen 5 times a week, from the age of 3 months until death. The treatment failed to have a significant influence on body weight dynamics or mean lifespan. However, sorbent-treated animals survived 4 months longer until 90% of them died. Although there were no significant differences in the frequency of either all or only malignant tumors between study group and controls, the former showed fewer multiple tumors (1.4 times) as well as a tendency of decreased incidence of neoplasms of the hemopoietic system and uterine polyps. Tumor-bearing sorbent-treated mice survived 4 months longer, while those with malignant tumors only survived 5 months longer (p < 0.05). The investigation failed to detect any carcinogenicity of Akvalen. It is suggested that the sorbent possesses certain geroprotective and anti-tumor properties.

Thromboembolism in patients with high-grade glioma.

OBJECTIVE: To identify factors related to increased or decreased risk of thromboembolism (TE) in patients with high-grade glioma. DESIGN: We performed a retrospective analysis of 64 patients enrolled in two prospective clinical trials of chemotherapy and radiation therapy for newly diagnosed high-grade glioma. MATERIAL AND METHODS: The 64 patients were 18 years of age or older and had histologically confirmed grade 3 or 4 astrocytoma, mixed astrocytoma-oligodendroglioma, or gliosarcoma. The diagnosis of TE was confirmed by impedance plethysmography, venography, duplex ultrasonography, ventilation-perfusion lung scanning, or pulmonary angiography. For statistical analysis, the study group was divided into those with and those without TE. RESULTS: TE developed in 18 of the 64 patients (28%). Of the 18 patients, 11 had deep venous thrombosis of a lower extremity, 5 had pulmonary emboli, and 2 had superficial thrombophlebitis. A paretic arm (P = 0.017), a paretic leg (P = 0.026), or a history of TE before the diagnosis of glioma (P = 0.076) was more common in patients with TE than in those without TE. Ten patients in the group without TE were using aspirin preoperatively in comparison with no patient in the TE group (P = 0.05). No significant differences were noted in duration of survival (median, 39.4 weeks and 46 weeks for the TE and non-TE groups, respectively). One patient with apparently excessive anticoagulation had a fatal intracerebral hemorrhage. CONCLUSION: This study suggests that TE in patients with newly diagnosed high-grade glioma might be associated with a history of TE or with a paretic extremity; however, no evidence of worse survival was noted in the TE group. Treatment with heparin followed by warfarin sodium was associated with infrequent bleeding complications. An intriguing finding was that the use of aspirin before operation was associated with a decreased risk of TE. Thus, a prospective study with use of aspirin in patients with high-grade glioma at risk for TE would be reasonable.

Mucociliary function following sinus mucosal regeneration.

To evaluate sinus mucosal regeneration and cilia motility after surgical removal, 15 rabbits underwent unilateral removal of maxillary sinus mucosa. The opposite sinus served as an unoperated control. After 10 weeks, specimens were taken for examination from all operated on and control sinuses. Light, dark-field, and electron microscopy were performed. Mucosa from eight of the 15 sinuses operated on showed ciliary regeneration by light microscopy; six of these exhibited motile cilia on dark-field examination. Histopathologic findings of marked fibrosis, decreased seromucinous glands, and significant inflammation were commonly present in the sinuses operated on. Electron microscopy revealed frequent abnormalities, including complex and edematous cilia and fewer than normal cilia per unit area compared to controls. The dark-field, light, and electron microscopic findings of the regenerated, post-surgical mucosa are discussed.

Olfactory neuroblastoma: clinicopathologic and immunohistochemical characterization of four representative cases.

Olfactory neuroblastomas are rare tumors whose clinical prognosis is not predictable by assessment of initial stage or grade. The pathologic diagnosis is often difficult because of the wide range of the patient's age and histologies. In this report, we document that the diagnosis of olfactory neuroblastoma can be clarified by immunohistochemical demonstration of a unique antigenic profile that can be obtained in routinely processed biopsies. We describe four cases of olfactory neuroblastoma diagnosed and treated from 1979 to 1989, each confirmed by immunohistology. One of our patients was misdiagnosed twice at an outside institution, first as having nasopharyngeal carcinoma and then as having small-cell, undifferentiated "oat cell" carcinoma. Despite accurate tumor diagnosis and appropriate therapy, we found that there was no apparent correlation of clinical outcome with Kadish clinical stage or histologic grade of tumor.

Abnormal coagulation profiles in tonsillectomy and adenoidectomy patients.

Preoperative coagulation profile screening is routinely performed in otolaryngology before tonsillectomy and adenoidectomy surgery in the United States. Recently there has been controversy as to whether this routine testing is necessary. To evaluate the need for this testing, we reviewed a series of patients with particular attention to abnormal coagulation profiles. Of 91 consecutive patients undergoing tonsillectomy, adenoidectomy, or both, four had abnormal preoperative coagulation profiles. Of these patients, one had von Willebrand disease, one had hypofibrinoginemia, and two had a transient acquired lupus-like anticoagulant. The latter condition, which causes a temporary prolongation of the activated partial thromboplastin time, is discussed in detail along with a review of the pertinent literature. We conclude that coagulopathies occur frequently enough to justify preoperative screening even in the absence of a positive history.

Thrombotic thrombocytopenic purpura: successful treatment unlocks etiologic secrets.

The cause of platelet agglutination in thrombotic thrombocytopenic purpura has been an enigma. Current evidence indicates that the interaction of platelets with a platelet-aggregating factor or unusually large multimers of factor VIII: von Willebrand factor, or both, may cause the abnormal platelet agglutination. Recent success in the treatment of thrombotic thrombocytopenic purpura with intravenous infusion of immunoglobulin suggests that the abnormal platelet agglutination in thrombotic thrombocytopenic purpura may reflect a deficiency of immunoglobulins that normally inhibit platelet-aggregating factors or large multimers of factor VIII: von Willebrand factor.

Cytodestructive mechanisms provoked by food antigens: III. Inhibition of direct and antibody-dependent allergic autocytotoxicity (ACT) by ketotifen.

In vitro challenge of peripheral white blood cells (WBC) from 15 food sensitive individuals and 16 asymptomatic controls was studied in allergic autocytotoxicity (ACT) assay using extracts of cow's milk, corn, and wheat. The observed disintegration of the WBC in the direct and antibody-dependent ACT was inhibited by ketotifen in a linear, dose-dependent manner. Therefore, our data demonstrate that the ACT response is associated with anaphylactic injury which is prevented by pretreatment with ketotifen, in vitro.