Forced expiratory flow in uninfected infants and children born to HIV-infected mothers

The Pediatric Pulmonary and Cardiovascular Complications of Vertically Transmitted HIV (P(2)C(2) HIV) Study is a multicenter study examining pulmonary and cardiac outcomes in offspring of HIV-infected mothers. This portion of the P(2)C(2) study tests the hypothesis that infants exposed to, but uninfected by, maternal HIV have normal maximal expiratory flow at functional residual capacity (V'max,(FRC)). We obtained 500 measurements of V'max,(FRC) by rapid thoracic compression in 285 children ages 6-30 mo in five U.S. centers. The data were compared with those from a healthy cohort of children described elsewhere. V'max,(FRC) rose with height in a linear relationship. The slope of the regression line in the exposed infants did not differ statistically from the slope in the comparison group, but the intercept was about 20% lower (p < 0.001). Height and weight were comparable in the two cohorts, and the differences between intercepts persisted after adjusting for birth weight and gestational age. However, maternal HIV infection cannot be assumed to be the cause as the cohorts may have differed in other variables, such as socioeconomic status and frequency of maternal smoking and drug use. Also, measurements varied substantially within and between our five centers, probably in part because of different racial and ethnic distributions. In summary, maternal HIV infection probably has only a modest effect, if any, on maximal expiratory flow at functional residual capacity in uninfected infants.

Stable laser-pulse propagation in plasma channels for GeV electron acceleration

To achieve multi-GeV electron energies in the laser wakefield accelerator (LWFA) it is necessary to propagate an intense laser pulse long distances in plasma without disruption. A 3D envelope equation for a laser pulse in a tapered plasma channel is derived, which includes wakefields and relativistic and nonparaxial effects, such as finite pulse length and group velocity dispersion. It is shown that electron energies of approximately GeV in a plasma-channel LWFA can be achieved by using short pulses where the forward Raman and modulation nonlinearities tend to cancel. Further energy gain can be achieved by tapering the plasma density to reduce electron dephasing.

Relativistic focusing and ponderomotive channeling of intense laser beams

The ponderomotive force associated with an intense laser beam expels electrons radially and can lead to cavitation in plasma. Relativistic effects as well as ponderomotive expulsion of electrons modify the refractive index. An envelope equation for the laser spot size is derived, using the source-dependent expansion method with Laguerre-Gaussian eigenfunctions, and reduced to quadrature. The envelope equation is valid for arbitrary laser intensity within the long pulse, quasistatic approximation and neglects instabilities. Solutions of the envelope equation are discussed in terms of an effective potential for the laser spot size. An analytical expression for the effective potential is given. For laser powers exceeding the critical power for relativistic self-focusing the analysis indicates that a significant contraction of the spot size and a corresponding increase in intensity is possible.

Thoracoabdominal compression and respiratory system compliance in HIV-infected infants

The thoracoabdominal compression technique (TAC) is used to measure expiratory flow in infants. We investigated whether TAC caused a change in total thoracic compliance (Crs), resistance (Rrs), and respiratory system time constant (Trs). We studied 41 infants (mean age, 12.4 mo; SD, 7.5) from five centers studying longitudinal lung and cardiovascular function of infants from HIV-infected mothers. We measured Crs, Rrs, and Trs before and after TAC. Changes in Crs, Rrs, and Trs after TAC were not dependent on the length of time since TAC. Crs and Trs were reduced after TAC, p = 0.013 and p = 0.003, respectively, whereas Rrs did not change. When compared with uninfected infants, HIV-infected infants had a larger post-pre TAC percent decline in Crs (p = 0.003) and a post-pre TAC rise in mean Rrs (p = 0.03). These differences remained significant after adjusting for sex and age. When performing infant pulmonary function testing, TAC itself produces a temporary decrease in Crs and Trs that is more significant in infants at risk for abnormal lung volume or compliance. Therefore, the sequence of performing the infant lung function parameters should be the same each time the testing is repeated with TAC as the last parameter tested at each testing session.

Transverse modulation of an electron beam generated in self-modulated laser wakefield accelerator experiments

Low energy electron beams (E approximately 300 keV) generated in a self-modulated laser wakefield accelerator experiment were observed to filament and be deflected away from the laser axis forming radial jets in the electron beam profile. At higher energies (E>900 keV), the filamentation and jets were suppressed and smooth electron beams copropagating with the laser were observed. The observed electron beam filamentation likely results from laser beam filamentation in the plasma due to relativistic self-focusing effects. The radial jets of low energy electrons are likely caused by transverse ejection of the electrons due to the radial structure of the wakefield and space charge deflection of electrons as they exit the laser focus.

Is laparoscopic approach to lumbar spine fusion worthwhile?

BACKGROUND

Laparoscopic lumbar spine fusion has been recently described. The aim of this study is to evaluate the safety and efficacy of this procedure for single- and multiple-level degenerative disc disease.

METHODS

Twenty-four consecutive laparoscopic interbody lumbar fusions were evaluated prospectively (18 single-level were compared with 6 multiple-level procedures). Results of the laparoscopic multiple-level procedures were further compared with 12 open multiple-level operations.

RESULTS

Twenty procedures were completed laparoscopically. The conversions were related to iliac vein lacerations (3 cases) and a mesenteric tear. Single-level cases had lower morbidity (22% versus 83%), shorter hospital stay (2 versus 10 days), and higher fusion rate (88% versus 50%) than multiple-level procedures. Overall results in the latter group were worse than in the matched open group.

CONCLUSIONS

Laparoscopic single-level fusion (L5-S1) is safe and carries the benefits of minimal access surgery. Morbidity after multiple level approach is high, and this procedure cannot be advocated at this time.

Analysis of Gaussian beam and Bessel beam driven laser accelerators

This paper presents a comparison of Gaussian and Bessel beam driven laser accelerators. The emphasis is on the vacuum beat wave accelerator (VBWA), employing two laser beams of differing wavelengths to impart a net acceleration to particles. Generation of Bessel beams by means of circular slits, holographic optical elements, and axicons is outlined and the image space fields are determined by making use of Huygens' principle. Bessel beams-like Gaussian beams-experience a Guoy phase shift in the vicinity of a focal region, resulting in a phase velocity that exceeds c, the speed of light in vacuo. In the VBWA, by appropriate choice of parameters, the Guoy phases of the laser beams cancel out and the beat wave phase velocity equals c. The particle energy gain and beam quality are determined by making use of an analytical model as well as simulations. The analytical model--including the v x B interaction--predicts that for equal laser powers Gaussian and Bessel beams lead to identical energy gains. However, three-dimensional, finite-emittance simulations, allowing for detuning, transverse displacements, and including all the electromagnetic field components, show that the energy gain of a Gaussian beam driven VBWA exceeds that of a Bessel beam driven VBWA by a factor of 2-3. The particle beam emerging from the interaction is azimuthally symmetric and collimated, with a relatively small angular divergence. A table summarizing the ratios of final energies, acceleration lengths, and gradients for a number of acceleration mechanisms is given.

High efficiency guiding of terawatt subpicosecond laser pulses in a capillary discharge plasma channel

Transmission efficiencies in excess of 75% were obtained in the optical guiding of subpicosecond, terawatt laser pulses in a 2-cm-long capillary discharge plasma channel at the Naval Research Laboratory. The guided laser beam size at the exit of the channel was measured using far field imaging and Thomson scattering techniques. The guided laser intensity was >1 x 10(17) W/cm(2) at a guided beam diameter of 35 microm for a propagation length of 22 Rayleigh ranges. There is evidence that the plasma channel extends beyond the ends of the capillary and affects the far field beam structure of the transmitted laser pulse.

Alveolar vascularization of the lung in a lamb model of congenital diaphragmatic hernia

Pulmonary hypoplasia and pulmonary hypertension are factors limiting the survival of infants with congenital diaphragmatic hernia (CDH). A reduction in the number of pre-acinar pulmonary vessels and increased muscularization are the structural lesions implicated as causes of irreversible hypoxemia. Whether there is a reduction in the number of air-blood barriers, which represent the capillary surface area of the lung involved in gas exchange, is unknown. We sought to determine if the lungs of CDH lambs have: (1) a reduction in total capillary surface area proportionate to the reduction in the total alveolar surface area of the lung; and/or (2) a disproportionate reduction in the number of capillaries (air blood barriers) within each acinus. The latter measurement was determined by calculating the capillary load which we defined as the number of air blood barriers/unit of surface density. At 80 d gestation (pseudoglandular period), a diaphragmatic hernia was created surgically in one lamb fetus of a twin gestation. At term, the fetuses were removed, the chests opened and the lungs fixed by a tracheal infusion of 1.5% glutaraldehyde at 25 cm of water pressure. Tissues from the lower lobes were examined by light and electron microscopy. Using computerized interactive morphometry, alveolar and capillary surface area, and capillary load were determined by intersection and point counting for the right and left lungs. The data show that the total alveolar surface area of the left CDH and control lungs were 1.8 +/- 0.8 m2 and 6.1 +/- 1.1 m2 (p < 0.01), respectively, and for the right CDH and control lungs 2.5 m2 +/- 0.1 and 11.2 +/- 1.9 m2 (p < 0.01), respectively. The total capillary surface area for the left CDH and control lungs were 0.7 +/- 0.3 m2 and 2.8 +/- 1.2 m2 (p < 0.05), respectively, and for the right CDH and control lungs 0.9 +/- 0.3 m2 and 3.8 +/- 1.5 m2 (p < 0.05), respectively. The capillary load was not statistically different. These findings demonstrate that the lungs in CDH are deficiently vascularized at the alveolar surface due to a reduction in the total alveolar surface area. Each acinus contains the same number of air blood barriers per unit of alveolar surface area indicating a normal acinar composition.

Risk factors for the development of obliterative bronchiolitis after lung transplantation

BACKGROUND

Acute rejection has emerged as an important risk factor for obliterative bronchiolitis after lung transplantation. We performed a multivariate analysis to assess the impact of additional variables.

METHODS

Seventy-four recipients (48 heart-lung, 18 single-lung, and 8 bilateral-lung recipients) who survived longer than 90 days and underwent transplantation more than 15 months before data analysis were included in this study. Several variables were entered into a Cox regression analysis to determine their association with the development of bronchiolitis obliterans syndrome.

RESULTS

Bronchiolitis obliterans syndrome developed in 48 (65%) of 74 patients. Significant correlations were detected for acute rejection score, defined as the sum of pathologic grades of each separate acute rejection episode (p = 0.0004, likelihood ratio test value = 12.4) and for lymphocytic bronchiolitis (p = 0.03). In a bivariate model, episodes of organizing pneumonia and bacterial or fungal pneumonia significantly increased the likelihood ratio test value of the acute rejection score. The addition of the cytomegalovirus infection score, reflecting the frequency and severity of infection, to the combination of the acute rejection score and episodes of bacterial or fungal pneumonia resulted in a further significant increase in the likelihood ratio test value. Significant risk factors for moderate to severe stages of airflow limitation were at least one episode of acute rejection of grade > or = 2, younger recipient age, and any acute rejection episode 180 days or longer after transplantation.

CONCLUSIONS

Increasing frequency and severity of acute rejection episodes are strongly associated with the development of bronchiolitis obliterans syndrome. Lymphocytic bronchiolitis appeared to be significant by univariate analysis, but in a two-risk factor model, it did not augment the influence of acute rejection. Organizing pneumonia, bacterial or fungal pneumonia, and increasing severity and frequency of cytomegalovirus infections potentiate the effect of acute rejection. Late episodes of acute rejection and younger recipient age increase the risk for development of advanced disease.

Backscattered supercontinuum emission from high-intensity laser-plasma interactions

We performed high-intensity subpicosecond laser-plasma interaction experiments to examine nonlinear scattering mechanisms in underdense plasmas. At incident laser intensities of 2 x 10(18) W/cm(2) the stimulated-Raman-backscattered spectrum exhibited an extremely broad, supercontinuumlike structure (Deltaomega/omega(0) > 1) extending from ~500 to >1200 nm (limited only by detector sensitivity). Large-amplitude modulations in the spectrum of the backscattered light were measured and are attributed to an interaction of the stimulated-Raman-scattered radiation with ion plasma waves.

Channeling of terawatt laser pulses by use of hollow waveguides

Subpicosecond laser pulses at power levels in excess of 1 TW were channeled through hollow microcapillary tubes by use of a combination of grazing-incidence dielectric and plasma-wall reflection mechanisms. Maximum input and output intensities were 10(17) and 10(16) W/cm(2) through 50-microm radius by 3-cm-long glass microcapillary tubes with as few as two waveguide modes being excited. 133-microm radius tubes as long as 13 cm resulted in successful channeling with an extinction coefficient of 0.2 cm(-1) and a plasma-wall reflectivity of 80%.

Effect of zidovudine on human fetal lung development

Zidovudine (AZT) is currently used to treat human immunodeficiency virus (HIV)-positive women during pregnancy to prevent the prenatal transmission of HIV type 1 (HIV-1). However, AZT not only inhibits HIV replication but also affects the DNA polymerases of human cells; hence AZT is not recommended during the first trimester of pregnancy. The lung is a unique organ because it continues to grow and develop throughout fetal life. Using a human fetal lung organ culture system, we sought to determine the effect of AZT on morphogenesis and epithelial cytodifferentiation of developing alveoli. Lung tissues from three fetuses, 14-15 weeks gestational age, were grown in culture for 24 hours (day 0). AZT at a concentration of either 0.4, 4.0, 8.0, or 40.0 mumol/L was added on days 1, 5, and 10 of growth. The cultures were interrupted on days 6 and 15 and examined by light and electron microscopy for alveolar saccular development, interstitial thinning, and epithelial cell differentiation. On day 6 of growth the treated cultures demonstrated fewer alveolar saccules and a thicker, more cellular interstitium compared to the controls. After 15 days of growth the cultures treated with 0.4 mumol/L of AZT appeared structurally similar to the controls. The cultures treated with AZT concentrations of 4.0 to 40.0 mumol/L appeared unchanged from day 6, implying arrested maturation of the culture. However, epithelial cell differentiation was unaffected. We conclude that AZT at concentrations of 4.0 mumol/L and greater affects the structural development of the human fetal lung in vitro.(ABSTRACT TRUNCATED AT 250 WORDS)

Production and characterization of human monoclonal lymphocytotoxic autoantibodies from a renal dialysis patient

We have produced human monoclonal lymphocytotoxic autoantibodies from a renal dialysis patient by the generation of a mouse/human heterohybridoma. The antibodies are of the IgM class and react with the patient's autologous cells, the B-lymphoblastoid cell line producing the antibody, normal T and B lymphocytes, B cells from chronic lymphatic leukemia patients (CLL cells), and the autoantibody-sensitive cell line K562. Screening of the monoclonal antibodies (mAb) against panels of normal T and B cells and CLL cells demonstrated that different reactivity profiles could be generated at different dilutions of the mAb. These profiles were identical to those seen with autoantibodies from different renal patients and this suggests that these profiles do not imply different antibody specificities but differing target cell sensitivity. Reactivity profiles seen in the fluorescence binding assays suggest that the target cell sensitivity is dictated not by antigen density alone but also by antibody/antigen affinity. The results from studies of enzyme treatment of target cells and lectin inhibition of the molecular specificity suggest that the autoantibodies are polyreactive, capable of binding sialic acid-dependent epitopes and other negatively-charged cell surface molecules.

The production of a human monoclonal antibody defining a split of HLA-DRw13 (DRw13b)

By use of the heterohybridoma technique we have produced a human monoclonal antibody (NDS40) which detects a split of HLA-DRw13 (DRw13b) which is in linkage with HLA-DQw1. In addition, the antibody reacts with cells positive for HLA-DRw8 and DRw11, but does not react with the commonly found split of DRw13 (DRw13a) which is associated with DQw1. NDS40 is cytotoxic and is of the lambda IgM class.

Capsulorrhaphy with a staple for recurrent posterior subluxation of the shoulder

Twenty athletes who had recurrent posterior subluxation of the shoulder, eight of whom also had associated anterior instability, were treated with capsulorraphy with a posterior staple. Nine patients had an unsatisfactory result: six had recurrence of the posterior instability and three still had moderate or severe pain. Five of six patients who had lax ligaments had a recurrence. Complications developed in five patients: pain from a staple in one, postoperative adhesions in two, and ectopic bone in two. Only one patient was able to throw as well as he had before the injury. Staple capsulorrhaphy is not acceptable treatment for posterior subluxation of the shoulder because it is associated with a high rate of failure and complications.

Triple therapy immunosuppression in cadaveric renal transplantation

One hundred and ninety-two patients received 200 consecutive cadaver renal transplants (158 first and 42 regrafts) and were treated with triple therapy immunosuppression consisting of low-dose cyclosporin, azathioprine and prednisolone. One-year patient and graft survival rates were 95% and 82%, respectively. Against this low rate of graft loss, the proportion of rejection-free patients in the first 3 months was strongly related to matching for HLA-DR (P less than 0.01), although HLA-DR matching was not associated with improved graft survival. More grafts were lost to nonimmunological causes than to rejection, and these losses fell into three main categories, namely, losses in elderly and diabetic patients and losses due to renal vascular thrombosis. Thus, triple therapy immunosuppression appears to offer effective immunosuppression, resulting in good graft and patient survival, especially in highly sensitised patients or patients receiving regrafts. There are relatively few serious adverse effects, although elderly and diabetic patients experienced significant morbidity and mortality after transplantation.