Comparison of surface integral equation formulations for electromagnetic analysis of plasmonic nanoscatterers

The performance of most widespread surface integral equation (SIE) formulations with the method of moments (MoM) are studied in the context of plasmonic materials. Although not yet widespread in optics, SIE-MoM approaches bring important advantages for the rigorous analysis of penetrable plasmonic bodies. Criteria such as accuracy in near and far field calculations, iterative convergence and reliability are addressed to assess the suitability of these formulations in the field of plasmonics.

Solution of large-scale plasmonic problems with the multilevel fast multipole algorithm

A surface integral equation together with the multilevel fast multipole algorithm is successfully applied to fast and accurate resolution of plasmonic problems involving a large number of unknowns. The absorption, scattering, and extinction efficiencies of several plasmonic gold spheres of increasing size are efficiently obtained solving the electric and magnetic current combined-field integral equation. The numerical predictions are compared with reference analytic results to demonstrate the accuracy, suitability, and capabilities of this approach when dealing with large-scale plasmonic problems.

Surface integral equation formulation for the analysis of left-handed metamaterials

A surface integral equation (SIE) formulation is applied to the analysis of electromagnetic problems involving three-dimensional (3D) piecewise homogenized left-handed metamaterials (LHM). The resulting integral equations are discretized by the well-known method of moments (MoM) and solved via an iterative process. The unknowns are defined only on the interfaces between different media, avoiding the discretization of volumes and surrounding space, which entails a drastic reduction in the number of unknowns arising in the numerical discretization of the equations. Besides, the SIE-MoM formulation inherently includes the radiation condition at infinity, so it is not necessary to artificially include termination absorbing boundary conditions. Some 3D numerical examples are presented to confirm the validity and versatility of this approach on dealing with LHM, also providing some intuitive verifications of the singular properties of these amazing materials.

Echocardiographic strain imaging to assess early and late consequences of sarcomere mutations in hypertrophic cardiomyopathy

BACKGROUND

Genetic testing identifies sarcomere mutation carriers (G+) before clinical diagnosis of hypertrophic cardiomyopathy (HCM), allowing characterization of initial disease manifestations. Previous studies demonstrated that impaired relaxation develops before left ventricular hypertrophy (LVH). The precise impact of sarcomere mutations on systolic function in early and late disease is unclear.

METHODS AND RESULTS

Comprehensive echocardiography with strain imaging was performed on 146 genotyped individuals with mutations in 5 sarcomere genes. Contractile parameters were compared in 68 preclinical (G+/LVH-), 40 overt (G+/LVH+) subjects with HCM, and 38 mutation (-) normal control relatives. All subjects had normal left ventricular ejection fraction. In preclinical HCM, global and regional peak systolic strain (epsilon(sys)) and longitudinal systolic strain rate were not significantly different from controls, but early diastolic mitral annular velocity (Ea) was reduced by 13%. In overt HCM, there was a significant 27% and 14% decrease in global longitudinal epsilon(sys) and systolic strain rate, respectively, compared with both preclinical HCM and controls (P<0.013 for all comparisons), and a 33% reduction in Ea.

CONCLUSIONS

Sarcomere mutations have disparate initial effects on diastolic and systolic functions. Preclinical HCM is characterized by impaired relaxation but preserved systolic strain. In contrast, both diastolic and longitudinal systolic abnormalities are present in overt disease despite normal ejection fraction. We propose that diastolic dysfunction is an early consequence of sarcomere mutations, whereas systolic dysfunction results from mutations combined with subsequent pathological remodeling. Identifying mechanistic pathways triggered by these mutations may begin to reshape the clinical paradigm for treatment, based on early diagnosis and disease prevention.

Predictive factors in advanced head and neck cancer treated by radio-chemotherapy and hypoxia modification

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Background: Anemia and tumor hypoxia are known factors for resistance to radio-chemotherapy (RT-CT). In a previous report we have suggested that spinal cord stimulation (SCS) can modify tumor oxygenation and regional blood flow in head and neck cancer (HNC). The aim of the present prospective study was to test the predictive value of pO2 measurement in HNC treated by RT-CT and hypoxia modification using SCS. Methods: Twelve male patients with advanced HNC were analyzed. Stage IVb-IVa: 8–4; mean age 58 + 7.6 years (46–70). Scheduled therapy was hyperfractionated RT (120 cGy/fraction, two fractions/day, total dose 81.6 Gy) from a Co- 60 source, and tegafur 800 mg/day. SCS devices were placed before RT-CT under local anesthesia. During treatment, SCS was connected from 20–30 min before to 20–30 min after each radiotherapy session. Before treatment, they were assessed: Hemoglobin levels and tumor oxygenation pre-SCS and pos-SCS (measured by a polarographic probe system ‘pO2 Histograph‘), expressed as median-pO2, and the fraction of pO2 values less than 5 mmHg (HF5) and less than 2.5 mmHg (HF2.5). Correlations were assessed using Pearson and Spearman tests, and actuarial survival using Kaplan-Meier estimates and Log-rank test. Results: Hemoglobin levels were correlated with oxygenation pre-SCS and pos-SCS: median-pO2 (p=0.005 and p=0.011), HF5 (p=0.048 and p=0.005) respectively. Anemia was associated with more advanced stage (IVb vs IVa, p=0.022), higher HF5 pos-SCS (p=0.028) and lower disease-free survival (p=0.019). The HF2.5 pos-SCS was adversely correlated with the 2 years actuarial: disease-free survival (p=0.027), cause-specific survival (p=0.008) and overall survival (p=0.008). HF2.5 was also correlated with hematocrit (p=0.044). Conclusions: Low hemoglobin levels and anemia are associated with more hypoxic and more advanced tumors. Pre-treatment tumor hypoxia (assessed by the fraction of pO2 values less than 2.5 mmHg during-SCS) is a strong predictive factor for survival in advanced HNC. Patients with highly hypoxic tumors should be selected for more aggressive treatments. Partially supported by: Grant ‘FUNCIS: PI 31–98‘. Scientific supervision was carried out by GICOR.

No significant financial relationships to disclose.

Effect of cervical spinal cord stimulation on regional blood flow and oxygenation in advanced head and neck tumours

BACKGROUND

Tumour ischaemia leads to decreased delivery of oxygen, chemotherapy and radiosensitisers. Hypoxia in head and neck (H&N) tumours is an important adverse prognostic factor. Spinal cord stimulation (SCS) is a well-established neurosurgical technique in the treatment of several ischaemic syndromes. This prospective study evaluated the effect of cervical-SCS on common carotid artery (CCA) blood flow and tumour oxygenation in patients with advanced H&N cancer.

PATIENTS AND METHODS

Sixteen patients with advanced H&N tumours were enrolled. Cervical-SCS devices were inserted subcutaneously prior to commencement of scheduled chemoradiotherapy. Pre- and post-SCS measurements were as follows: (i) tumour oxygenation (mmHg) using polarographic probes; (ii) blood flow quantification (ml/min) and diastolic and systolic velocimetry (cm/s) in the CCA using colour Doppler.

RESULTS

After SCS, median tumour oxygenation increased in two-thirds of patients (34%; P = 0.023), all patients had improved CCA blood flow (50%; P <0.001) and almost all patients showed an increased CCA diastolic velocity (26%; P = 0.003) and systolic velocity (20%; P = 0.011).

CONCLUSIONS

Cervical-SCS increased tumour oxygenation and CCA blood flow, and could enhance the loco-regional delivery of oxygen, radiosensitising and chemotherapeutic drugs. Cervical-SCS as adjuvant in chemoradiotherapy of these tumours warrants further investigation.

Chimeric synthetic peptides from the nucleocapsid p24 protein of human immunodeficiency virus type-1

Two chimeric synthetic peptides incorporating antigenic sequences from N-terminal (peptide C14) (134-163) and C-terminal (peptide C15) (335-364) of the p24 protein of human immunodefiency virus (HIV- 1), were synthesized. Peptides C14-GG-C15 and C15-GG-C14 represented sequences from the p24 protein in both possible orders, separated by two glycine residues as arm spacers. These peptides were evaluated as antigen in an Ultramicroenzyme-linked immunosorbent assay (UMELISA) using sera of HIV-1-infected individuals (n = 16) with different titers of antibodies and the specificity was evaluated with healthy blood donors (n = 20). The results were compared to plates coated with monomeric peptides C14 and C15. The chimeric peptide C14-GG-C15 was the most antigenic. Those results may be related to the peptide structure, the sequence order in the chimeric peptide, and epitope accessibility to the antibodies. This chimeric peptide would be very useful for HIV-1 diagnostics.

Hepatitis B virus exposure in human immunodeficiency virus seropositive Cuban patients

In order to estimate the prevalence of serological markers of exposure to Hepatitis B Virus (HBV), 295 subjects were selected at random from the National Registry of human immunodeficiency virus positive subjects. Evidence of exposure to HBV was defined as: testing Hepatitis B surface antigen (HBsAg) and anti-Hepatitis B core antigen (anti-HBc) positive or anti-HBc positive only. Overall, 133 (45.5%) were positive for anti-HBc and 15 (5.1%) resulted positive to HBsAg. Significant statistical association was found between male sex and exposure to HBV (p<0.01). Homosexual or bisexual behavior was found to be strongly associated to HBV exposure (p<0.001). In conclusion, the prevalence of HBV serological markers is higher in Cuban HIV positive subjects compared to the Cuban general population.

[Facial nerve anomaly. A morphohistological study. Apropos a case]

A malformation of the facial nerve in the temporal bone of an otherwise normal adult is reported. The abnormality consisted in the facial nerve obstructing the oval window in the second part of its intrapetrosal section.

[Polyps, nodules, and Reinke edema. An epidemiological and histopathological study]

A retrospective epidemiological and histopathological review was made of 258 patients. Forty had laryngeal polyps, 35 vocal fold nodules, and 41 Reinke edema. One hundred forty-two records were excluded for lack of epidemiological or histopathological data. No dysplastic changes were observed in nodules or polyps. One patient with edema had mild dysplasia. The epidemiological data showed that voice abuse or misuse was the main factor in patients with vocal fold nodules; smoking was the main factor in polyps and edema.

Circulating cell adhesion molecules are correlated with ultrasound-based assessment of carotid atherosclerosis

Although cellular adhesion molecules (CAMs) are hypothesized to play an important role in atherogenesis, the relationship between CAMs and systemic atherosclerosis is uncertain. Among 92 outpatients (48 men; mean+/-SD age, 65+/-9 years), we evaluated the association of soluble vascular CAM-1 (sVCAM-1) and intercellular adhesion molecule-1 (sICAM-1) with carotid intimal-medial thickness (IMT), an index of early atherosclerosis. All subjects underwent a 2-dimensional ultrasound examination of both carotid arteries at the distal common carotid arteries and bifurcation. sVCAM-1 and sICAM-1 levels measured by enzyme-linked immunosorbent assay were significantly correlated with mean IMT of the common carotid artery (r=0.34 and r=0.30, respectively; P<0.01) and carotid bifurcation (r=0.31 and r=0.26, respectively; P<0.05), whereas sVCAM-1 was also positively associated with maximal carotid IMT (r=0.35, P<0.01). Adjustment for age attenuated the association between sVCAM-1 and common (r=0.16, P=0.13) and bifurcation (r=0.18, P=0.07) carotid IMT but had minimal effect on the associations between sICAM-1 and carotid measurements (r=0.32, P<0.01; r=0.23, P<0.05; for common and bifurcation IMT, respectively). Age-adjusted sICAM-1 levels increased in a stepwise fashion across common carotid IMT tertiles (253+/-27 versus 275+/-24 versus 384+/-26 pg/mL for the lowest, intermediate, and highest IMT tertiles, respectively; P<0.01). A similar trend was also found between sVCAM-1 levels and common carotid IMT tertiles (625+/-60 versus 650+/-53 versus 714+/-58 pg/mL; P<0.15). These associations were minimally affected in analyses adjusting for hypertension, diabetes, smoking, low and high density lipoprotein cholesterol, lipoprotein(a), and homocysteine, or in a subgroup analysis limited to those with no prior history of atherothrombotic disease. These data demonstrate a positive association between serum CAMs with carotid IMT and further support the hypothesis that systemic inflammation may have a role in atherosclerotic lesion development.

Influence of mechanical ventilation on blood lactate in patients with acute respiratory failure

OBJECTIVES

To determine whether mechanical ventilation (MV) may affect blood lactate concentration in patients with acute respiratory failure.

DESIGN

Prospective observational study with follow-up to hospital discharge.

SETTING

A 17-bed medical and coronary intensive care unit in a 650-bed general hospital.

PATIENTS

55 adult patients mechanically ventilated for acute respiratory failure between May 1996 and April 1997 were recruited.

MEASUREMENTS AND RESULTS

Arterial blood samples for determination of plasma lactate and blood gas analysis were taken just before tracheal intubation on spontaneous breathing, and 20 and 60 min after the initiation of controlled MV. Cuff systemic arterial pressure was measured before tracheal intubation and every 10 min during the first h of MV. Hyperlactatemia (arterial blood lactate > or = 2 mmol/l) was present in 21 of the 55 patients studied. After 20 min of MV, there was a decrease in blood lactate from 4.74 +/- 1.78 to 3.07 +/- 1.69 mmol/l (p < 0.01); 40 min later there was a further decrease to 2.63 +/- 1.35 mmol/l (p < 0.05). The decrease in blood lactate was also observed in those patients who after starting MV developed systemic arterial hypotension (p < 0.01). In patients with a normal lactate concentration at the entry to the study, lactate remained the same after 60 min on MV (NS).

CONCLUSIONS

Controlled MV decreases substantially the severity of hyperlactatemia in patients with acute respiratory failure, and any adverse circulatory effects of MV do not alter this beneficial outcome.

[Follow-up serological study of herpes simplex and cytomegalovirus in Cuban patients infected with human immunodeficiency virus (HIV)]

The evolution serological response against the herpes simplex virus and citomegalovirus in HIV infected patients grouped into different stages of the disease was studied. Fluctuations in the TPG of antibodies were observed in these values in a cyclical way through time. There was a greater significant difference among the TPG of antibodies against HSV in the group of asymptomatic patients compared with AIDS patients and with those who died. There is a marked decrease in the TPG of antibodies against HSV and CMV approximately one year before the death of patients.

Evaluation of the serologic response against two consensus V3 loop peptides from human immunodeficiency virus-1 in Cuban patients

OBJECTIVES

A retrospective study was conducted to evaluate the antibody response of Cuban patients infected with human immunodeficiency virus (HIV)-1 against two consensus peptides from the third variable domain (V3) loop of glycoprotein gp120.

METHODS

The study included sera from 10 individuals at different stages of disease. Two 15-meric synthetic peptides designed from a consensus sequence, belonging to group B or C of HIV-1, were used to determine antibody titers and avidity indexes in an indirect enzyme-linked immunoassay.

RESULTS

A high reactivity against both peptides was detected, with 80% of the sera reacting with at least one of the peptides. The antibody titers and avidity indexes did not correlate with disease progression. Additionally, for one of the patients from whom the virus had been isolated, a higher avidity index was found against the homologous peptide.

CONCLUSIONS

This study showed high reactivity against two consensus peptides from the V3 loop of gp120 among patients with HIV. Large scale studies are needed to determine whether the titers or avidity of anti-V3 antibodies, at the early stages of infection, are predictive of disease progression. Both peptides are candidates for inclusion in experimental vaccines.

Use of antipsychotic drugs in nursing homes: current compliance with OBRA regulations

OBJECTIVE

To examine the degree and patterns of compliance with the Omnibus Budget Reconciliation Act (OBRA) regulations regarding the use of antipsychotic drugs in nursing homes.

DESIGN

Retrospective chart review of all resident records.

PARTICIPANTS

Eight nursing homes: five community, two county-owned, and one university-affiliated Veterans Administration facility.

MEASUREMENTS

A structured assessment instrument to track compliance with each aspect of the OBRA regulations regarding antipsychotic drug use.

RESULTS

A total of 1573 nursing home residents' pharmacy records were reviewed between August 1994 and March 1996. Two hundred seventy-nine residents were actively taking antipsychotic medications (prevalence = 17.7%). Mean compliance greater than 70% was found for (1) appropriate diagnostic indication (mean = 70.9%), (2) dosage within recommended limits (mean = 90.1%), and 3) documented appropriate target symptoms (mean = 90.4%). Dosages were more likely to exceed limits in those patients with histories of major mental illness, particularly schizophrenia.

CONCLUSIONS

Nursing homes were better able to comply with those guidelines that are most specific. Educational interventions now need to focus on behavioral interventions, monitoring of adverse effects, and efficacy. These data are useful in establishing threshold levels of performance and can be used by nursing homes for continuous quality improvement. OBRA continues to impact neuroleptic drug prescribing practices in nursing homes significantly.

A recombinant protein based immunoassay for the combined detection of antibodies to HIV-1, HIV-2 and HTLV-I

The aim of this study was to develop and evaluate a combined assay for the detection of antibodies to HIV-1, HIV-2 and HTLV-I (human T-cell leukemia virus type I). A mixture of recombinant proteins and synthetic peptides was fixed to the surface of microELISA wells and a protein A peroxidase conjugate was used as tracer. The combined assay was compared to specific HIV-1/2 and HTLV-I commercial ELISAs. The sensitivity was studied with a panel of 158 HIV-1, 82 HIV-2 and 48 HTLV-I positive sera, all of which were reactive in the combined assay. The analytical sensitivity was studied with a panel of serially diluted sera and was similar to that obtained for the specific ELISAs. The specificity of the test was 99.78% against a panel of 466 negative sera collected from voluntary donors that included HBsAg, HCV, and VDRL positive sera. The false positive serum was borderline in the HTLV-I specific ELISA. The new combined ELISA can be used as an efficient initial screening assay, avoiding the cost of individual tests for HIV and HTLV.

Long-term treatment with recombinant interferon alpha-2b prolongs survival of asymptomatic HIV-infected individuals

RATIONALE AND OBJECTIVE

Early long-term treatment with recombinant interferon (IFN) alpha-2b delayed disease progression in asymptomatic Human Immunodeficiency Virus (HIV) carriers in a randomized trial that lasted from October 1987 to February 1992 (14). The aim of the work reported in this paper was to observe if there was also an effect on survival when the same patients were followed-up further.

DESIGN AND INTERVENTIONS

IFN alpha-2b was given 3 x 10(6) IU, 3 times weekly. The control group did not receive any treatment. The main end-point for this evaluation was death due to any cause. The deadline was August 1995.

POPULATION

Subjects were anti-HIV-1 seropositive, Western blot-confirmed, asymptomatic (CDC group II), or with generalized lymphadenopathies (CDC group III). The groups had 79 (control) and 83 (IFN) patients.

MAIN RESULTS

Mean survival was longer in the IFN group (95% CI: 127-152 vs. 101-120 months since infection or 80-90 vs. 70-82 months since the start of treatment). Survival rates were higher in IFN-treated individuals (61-77% vs. 24-54% at 10 years of infection or 53-69% vs. 34-52% at 7 years of treatment or follow-up). It was also confirmed that disease progression is significantly slower in IFN-treated patients. There were 23.4 vs. 3.2% long-term survivors in the IFN and control groups, respectively (p = 0.005). IFN-treated patients had fewer AIDS-related malignancies (5 vs. 11), mainly Kaposi's sarcomas (1 vs. 5). This difference was not statistically significant, but clinically interesting. There was no difference in survival if measured since the onset of AIDS.

CONCLUSION

IFN alpha treatment given from the early stages of infection, but not after the appearance of AIDS symptoms, can prolong survival.

Single point dilution method for the quantitative analysis of antibodies to the gag24 protein of HIV-1

In the present work a concept proposed in 1992 by Dopotka and Giesendorf was applied to the quantitative analysis of antibodies to the p24 protein of HIV-1 in infected asymptomatic individuals and AIDS patients. Two approaches were analyzed, a linear model OD = b0 + b1.log(titer) and a nonlinear log(titer) = alpha.OD beta, similar to the Dopotka-Giesendorf's model. The above two proposed models adequately fit the dependence of the optical density values at a single point dilution, and titers achieved by the end point dilution method (EPDM). Nevertheless, the nonlinear model better fits the experimental data, according to residuals analysis. Classical EPDM was compared with the new single point dilution method (SPDM) using both models. The best correlation between titers calculated using both models and titers achieved by EPDM was obtained with the nonlinear model. The correlation coefficients for the nonlinear and linear models were r = 0.85 and r = 0.77, respectively. A new correction factor was introduced into the nonlinear model and this reduced the day-to-day variation of titer values. In general, SPDM saves time, reagents and is more precise and sensitive to changes in antibody levels, and therefore has a higher resolution than EPDM.

Cytotoxicity of a low molecular weight fraction from Aloe vera (Aloe barbadensis Miller) gel

The cytotoxicity of a low mol. wt fraction (LMWF) obtained from Aloe vera gel was determined by two different assays. Firstly, exposure of monolayers of chicken fibroblasts to LMWF induced disruption of intercellular junctions and detachment of individual cells from the bottom of the flask, with formation of cell-free gaps in the monolayer. Secondly, LMWF inhibited the production of reactive oxygen species by human polymorphonuclear leukocytes stimulated by zymosan, as followed by luminol-dependent chemiluminescence. The toxic activity of LMWF was compared to that of sodium dodecyl sulfate (a well-known toxic substance), aloe-emodin and aloin (an anthraquinone and its precursor present in Aloe vera cortex) using the chemilumescence assay, and was found to be of similar potency to these toxic substances on a weight-to-weight basis. These results confirm that Aloe vera gel contains toxic low mol. wt compounds, and every effort must be made to limit the amount of these toxins in the commercially prepared Aloe vera gel products.

Incidence of dehiscences in the fallopian canal

Fifty human temporal bones from necropsies were used to study the frequency of canal dehiscences in detail along the course of the facial nerve. Specifically, the study focused on bony dehiscences in the fallopian canal and vascular communications between the facial nerve and the surrounding bone. High frequency of dehiscences at the oval window (60%) and in the pyramidal segment (54%) were found. These dehiscence rates are in agreement with published reports. A 20% rate of dehiscences at the most anterior segment of the tympanic segment was noted and a non-reported high rate (20%) of multiple dehiscences along the course of the fallopian canal in the same temporal bone in specimens of newborns and young children. The significance of these findings in terms of clinical implications is discussed.