Many-body theory calculations of positronic-bonded molecular dianions

The energetic stability of positron-dianion systems [A-; e+; A-] is studied via many-body theory, where A- includes H-, F-, Cl-, and the molecular anions (CN)- and (NCO)-. Specifically, the energy of the system as a function of ionic separation is determined by solving the Dyson equation for the positron in the field of the two anions using a positron-anion self-energy as constructed in Hofierka et al. [Nature 606, 688 (2022)] that accounts for correlations, including polarization, screening, and virtual-positronium formation. Calculations are performed for a positron interacting with H22-, F22-, and Cl22- and are found to be in good agreement with previous theory. In particular, we confirm the presence of two minima in the potential energy of the [H-; e+; H-] system with respect to ionic separation: a positronically bonded [H-; e+; H-] local minimum at ionic separations r ∼ 3.4 Å and a global minimum at smaller ionic separations r ≲ 1.6 Å that gives overall instability of the system with respect to dissociation into a H2 molecule and a positronium negative ion, Ps-. The first predictions are made for positronic bonding in dianions consisting of molecular anionic fragments, specifically for (CN)22- and (NCO)22-. In all cases, we find that the molecules formed by the creation of a positronic bond are stable relative to dissociation into A- and e+A- (positron bound to a single anion), with bond energies on the order of 1 eV and bond lengths on the order of several ångstroms.

Many-Body Theory Calculations of Positron Scattering and Annihilation in H_{2}, N_{2}, and CH_{4}

The recently developed ab initio many-body theory of positron molecule binding [22J. Hofierka et al., Many-body theory of positron binding to polyatomic molecules, Nature (London) 606, 688 (2022)NATUAS0028-083610.1038/s41586-022-04703-3] is combined with the shifted pseudostates method [A. R. Swann and G. F. Gribakin, Model-potential calculations of positron binding, scattering, and annihilation for atoms and small molecules using a Gaussian basis, Phys. Rev. A 101, 022702 (2020)PLRAAN2469-992610.1103/PhysRevA.101.022702] to calculate positron scattering and annihilation rates on small molecules, namely H_{2}, N_{2}, and CH_{4}. The important effects of positron-molecule correlations are delineated. The method provides uniformly good results for annihilation rates on all the targets, from the simplest (H_{2}, for which only a sole previous calculation agrees with experiment), to larger targets, where high-quality calculations have not been available.

Bluetongue Disease Control in Northern Ireland During 2017 and 2018

Since the emergence of bluetongue virus in central and northern Europe in 2006, Northern Ireland's (NI) surveillance programme has evolved to include the use of risk assessments and simulation models to monitor the risk of bluetongue incursion. Livestock production is of high economic importance to NI as it exports approximately 75% of its agricultural produce. Its surveillance programme is designed to enable effective mitigation measures to be identified to minimize disease risk, and to provide additional assurances to protect NI's export markets in the European Union (EU) and third countries. Active surveillance employs an atmospheric dispersion model to assess the likelihood of wind-borne midge transfer from Great Britain (GB) to NI and to identify high risk areas. In these areas, the number of cattle tested for bluetongue is proportionally increased. Targeted surveillance is directed to ruminants imported from restricted countries and regions at risk of bluetongue. Targeted surveillance on high risk imports assists in early detection of disease as, despite all controls and preventive measures, legally imported animals may still carry the virus. In November 2018, a bluetongue-positive heifer was imported into NI. A case specific risk assessment was commissioned to estimate the likelihood of spread of bluetongue as a result of this incursion. November is the tail end of the midges' active period and therefore there was considerable uncertainty pertaining to the survival of midges inside a cattle shed and the potential for incubation of the virus in the vectors. An evidenced-based approach was adopted where temperature and midge abundance was monitored in order to minimize uncertainty and give an accurate estimate of the likelihood of virus spread to other animals following the arrival of the positive heifer. The heifer was destroyed and the evidence indicated that the risk of successful completion of the extrinsic cycle within the local midge population was negligible. This paper describes NI's surveillance programme between January 2017 and December 2018 and the case of a positive imported animal into the country. The importance of effective surveillance in early detection of threats and the usefulness of risk assessments is highlighted through the case study.

The Electrical Activity at Twin Boundaries in Silicon

Although coherent twin boundaries in silicon are electrically inactive, dislocations in the boundaries can act as efficient recombination centers for minority carriers. Different twin boundary dislocation arrangements have been studied by EBIC and TEM. It is found that the observed EBIC contrast is dependent not only on the arrangement of the dislocations in the boundaries but also on the inclination of the boundaries to the surface. It is shown that different defect configurations can produce similar EBIC contrast.

A NEW FORM OF DIFFERENTIAL MICRORESPIROMETER

1. A microrespirometer suitable for measuring oxygen uptakes from 0.1 to 10λ per hour is described. 2. The sensitivity of the instrument may be readily altered by substituting different sizes of capillary tubing. 3. By means of replaceable brass plugs the chamber volume of this instrument may be varied from 700 to less than 40λ. 4. No thermostat is required for the operation of the instrument at room temperature. 5. It may be charged at one temperature and used at a widely different one. 6. The chambers may be filled with any desired gas mixture. 7. Two solutions may be mixed during the course of an experiment. 8. The entire apparatus may be sterilized.

Effect of supplemental translaminar facet screw fixation on the stability of stand-alone anterior lumbar interbody fusion cages under physiologic compressive preloads

STUDY DESIGN

A biomechanical study of lumbar threaded interbody cage construct under varying compressive preloads of similar magnitudes to those experienced in vivo during daily activities.

OBJECTIVES

To test the hypothesis that supplemental translaminar facet screws would enhance the stability (ability to reduce segmental angular motion) of threaded interbody cages in flexion-extension during activities in which the spine is subjected to low compressive preloads, and therefore the stand-alone interbody cage construct is least stable.

SUMMARY OF BACKGROUND DATA

Controversy exists over whether threaded anteriorly placed interbody cages can be routinely used as "stand-alone" devices or whether they require supplemental posterior stabilization to achieve successful fusion. Biomechanical studies suggest that under conditions of low preloads, the motion segment treated with stand-alone cages might be less stable, particularly in extension. METHODS.: Eight human lumbar spine specimens (from L1 to sacrum) were tested intact, after insertion of 2 threaded cylindrical cages (BAK) at L5-S1 and after supplemental translaminar facet screw fixation. They were subjected to flexion and extension moments under progressively increasing magnitude of externally applied compressive follower preload from 0 to 1200 N. The range of angular motion in flexion-extension at L5-S1 was analyzed to assess the effect of translaminar facet screws on the stability of the cage construct for different compressive preloads.

RESULTS

In flexion, over 0 to 400 N preload, the supplemental translaminar facet screw fixation reduced the L5-S1 angular motion relative to intact by 71% to 74% as compared to 40% to 44% for the cages alone. This difference was statistically significant (P < 0.05). In extension at 0 N preload, the cages allowed more angular motion than the intact segment, whereas with translaminar facet screw fixation, the motion was reduced to the level of the intact segment. At 400 N preload, supplemental TLFS fixation significantly increased the stability of the cages, reducing the extension angular motion by 60% of intact (P = 0.04). Supplemental translaminar facet screw fixation did not significantly increase the stability provided by the cages in flexion or extension at the 1200 N preload magnitude.

CONCLUSIONS

In vivo during activities of daily living, interbody cage constructs are subject to varying compressive preloads due to external loads generated by paraspinal musculature, and our results suggest that the stability created by the cage (reduction in segmental angular motion) is not constant. The cage construct is likely to be least stable in extension during activities that impart low compressive preloads to the lumbar spine. Supplemental translaminar facet screw fixation will enhance stability of the motion segment treated with threaded cages, particularly during conditions of low compressive preloads, the very condition in which the cage alone is least effective in providing stability.

Compressive preload improves the stability of anterior lumbar interbody fusion cage constructs

BACKGROUND

Insertion of an anterior lumbar interbody fusion cage has been shown to reduce motion in a human spine segment in all loading directions except extension. The "stand-alone" cages depend on compressive preload produced by anular pretensioning and muscle forces for initial stabilization. However, the effect that the in vivo compressive preload generated during activities of daily living has on the construct is not fully understood. This study tested the hypothesis that the ability of the cages to reduce the segmental motions in flexion and extension is significantly affected by the magnitude of the externally applied compressive preload.

METHODS

Fourteen specimens from human lumbar spines were tested intact and after insertion of two threaded cylindrical cages at level L5-Sl. They were subjected to flexion and extension moments under progressively increasing magnitudes of externally applied compressive follower preload from 0 to 1200 N. The range of motion at level L5-S1 after cage insertion was compared with the value achieved in the intact specimens at each compressive preload magnitude.

RESULTS

The cages significantly reduced the L5-S1 flexion motion at all preloads (p < 0.05). They decreased flexion motion by 29% to 43% of that of the intact specimens for low preloads (0 to 400 N) and by 69% to 79% of that of the intact specimens under preloads of 800 to 1200 N. In extension, in the absence of an externally applied preload, the cages permitted 24% more motion than the intact segment (p < 0.05). In contrast, they reduced the extension motion at preloads from 200 to 1200 N. Under preloads of 800 to 1200 N, the reduction in extension motion after cage placement was 42% to 48% of that of the intact segment (p < 0.05). The reduction of motion in both flexion and extension after cage placement was significantly greater at preloads of 800 to 1200 N compared with the motion reductions at preloads of < or =400 N (p < 0.05).

CONCLUSIONS

In contrast to the observed extension instability under anular tension preload only, the two-cage construct exerted a stabilizing effect on the motion segment (a reduction in segmental motion) in flexion as well as extension under externally applied compressive preloads of physiologic magnitudes. The external compressive preload significantly affected the stabilization provided by the cages. The cages provided substantially more stabilization, both in flexion and in extension, at larger preloads than at smaller preloads.

CLINICAL RELEVANCE

The study suggests that the segment treated with an anterior lumbar interbody fusion cage is relatively less stable under conditions of low external compressive preload. The magnitude of preload required to achieve stabilization with stand-alone cages may be only partially achieved by anular pretensioning. Since the magnitude of the preload across the disc space due to muscle activity can vary with activities of daily living, supplemental stabilization of the cage construct may provide a more predictably stable environment for lumbar spine fusion.

Oral vitamin B12 can change our practice

Oral vitamin B12 can provide an effective alternative to intramuscular injections, so giving patients a choice and reducing costs in primary care. This study investigated the effectiveness, safety, and acceptability of oral vitamin B12 as replacement therapy in patients with vitamin B12 deficiency in a city general practice population. Forty patients previously maintained on vitamin B12 injections were given 1000 micro g of oral cyanocobalamin daily for up to 18 months. All the patients maintained satisfactory serum B12 levels and showed normal haematology and neurology. Compliance and acceptability was excellent. The time for a change in practice has indeed arrived.

The health burden of breast hypertrophy

Women seeking consultation for the surgical relief of symptoms associated with breast hypertrophy have been the focus of many studies. In contrast, little is known about those women with breast hypertrophy who do not seek symptomatic relief. The purpose of this study was to describe the health burden of breast hypertrophy by using a set of validated questionnaires and to compare women with breast hypertrophy who seek surgical treatment with those who do not. In addition, this latter group was compared with a group of control women without breast hypertrophy. Women seeking consultation for surgery were recruited from 14 plastic-surgery practices. Control subjects were recruited by advertisements in primary-care offices and newspapers. Women were asked to complete a self-report questionnaire that included the European Quality of Life (EuroQol) questionnaire, McGill Pain Questionnaire, Multidimensional Body Self Relations Questionnaire (MBSRQ), the Short Form-36 (SF-36) questionnaire, and questions regarding breast-related symptoms, comorbidities, and bra size. Descriptive statistics were compiled for three groups of women: (1) hypertrophy patients seeking surgical care, (2) hypertrophy control subjects (those whose reported bra-cup size was a D or larger), and (3) normal control subjects (those whose reported bra-cup size was an A, B, or C). The multiple linear regression method was used to compare the health burdens across groups while adjusting for other variables. Two hundred ninety-one women seeking surgical care and 195 control subjects were enrolled in the study. The 184 control subjects with bra-cup information available were further separated into 88 hypertrophy control subjects and 96 normal control subjects. In the control group, bra-cup size was correlated with health-burden measures, whereas in the surgical candidates, it was not. When scores were compared across the three groups, significant differences were found in all health-burden measures. The surgical candidates scored more poorly on the EuroQol utility, McGill pain rating index, MBSRQ appearance evaluation, physical component scale of the SF-36, and on breast symptoms than did the two control groups. In addition, the hypertrophy control subjects scored more poorly than the normal control subjects. With multiple linear regression analysis incorporating important potential confounders, the poorer scores in the surgical candidates remained statistically significant. It was concluded that breast hypertrophy in those seeking surgical care and those not seeking surgery has a significant impact on women's quality of life as measured by validated and widely used self-report instruments including the EuroQol, MBSRQ, McGill Pain Questionnaire, and the SF-36. Likewise, a new assessment instrument for breast-related symptoms also demonstrated greater symptomatology in women with breast hypertrophy.

Aspergillus fumigatus infection in a mega prosthetic total knee arthroplasty: salvage by staged reimplantation with 5-year follow-up

Fungal infection after total joint arthroplasty is an extremely serious complication and a challenge to the treating physician. When a fungal infection is compounded by a massive allograft or a metallic segmental replacement of the femur or other long bone, treatment options become increasingly limited and commonly have led to arthrodesis or amputation of the infected limb. We present the first case report of a low-grade osteosarcoma treated with a segmental distal femoral allograft prosthetic composite knee arthroplasty, which was complicated by infection with Aspergillus fumigatus. This complication was treated successfully with a staged reimplantation procedure, intravenous amphotericin, and oral fluconazole suppression. At 5 years after reimplantation, the patient has had no evidence of infection, no pain, and excellent range of motion without extensor lag. The Knee Society knee score improved from 50 to 100, and the function score improved from 40 to 100 (for both scores, 100 is the maximum).

Receptor-selective variants of human vascular endothelial growth factor. Generation and characterization

Vascular endothelial growth factor (VEGF) is a pleiotropic factor that exerts a multitude of biological effects through its interaction with two receptor tyrosine kinases, fms-like tyrosine kinase (Flt-1) or VEGF receptor 1 and kinase insert domain-containing receptor (KDR) or VEGF receptor 2. Whereas it is commonly accepted that KDR is responsible for the proliferative activities of VEGF, considerable controversy and uncertainty exist about the role of the individual receptors in eliciting many of the other effects. Based on a comprehensive mutational analysis of the receptor-binding site of VEGF, an Flt-1-selective variant was created containing four substitutions from the wild-type protein. This variant bound with wild-type affinity to Flt-1, was at least 470-fold reduced in binding to KDR, and had no activity in cell-based assays measuring autophosphorylation of KDR or proliferation of primary human vascular endothelial cells. Using a competitive phage display strategy, two KDR-selective variants were discovered with three and four changes from wild-type, respectively. Both variants had approximately wild-type affinity for KDR, were about 2000-fold reduced in binding to Flt-1, and showed activity comparable with the wild-type protein in KDR autophosphorylation and endothelial cell proliferation assays. These variants will serve as useful reagents in elucidating the roles of Flt-1 and KDR.

The effect of kyphosis on the mechanical strength of a long-segment posterior construct using a synthetic model

STUDY DESIGN

This experimental study used synthetic spine models to compare the effect of the angle of kyphosis, rod diameter, and hook number on the biomechanical stiffness of a long-segment posterior spinal construct.

OBJECTIVE

To examine the biomechanical effects of incremental kyphosis on variously instrumented long-segment posterior spinal constructs.

SUMMARY OF BACKGROUND DATA

Euler's formula for loading of curved long columns would suggest that kyphosis has a profound impact on the biomechanical behavior of long-segment posterior spinal constructs. The effects of sagittal contour on the mechanical properties of long-segment posterior spinal constructs have not been well documented.

METHODS

Kyphotic and straight synthetic spine models were used to test long-segment posterior instrumentation constructs biomechanically while varying rod diameter and the number of hook sites. The synthetic spines, composed of polypropylene vertebral blocks and isoprene elastomer intervertebral spacers, were fabricated with either 0 degrees, 27 degrees, or 53 degrees of sagittal contour. The models were instrumented with 5.5- or 6.35-mm titanium rods, and with either 8 or 12 hooks. The models were loaded from 0 to 300 N in a cyclical ramp fashion using an MTS 858 Bionix testing device testing device. Construct stiffness (force and displacement) during axial compression was determined.

RESULTS

Straight model: Changing the hook number from 8 to 12 caused a 32% increase in construct stiffness with the 5.5-mm rod. Changing the rod diameter from 5.5 to 6.35 mm caused a 36% increase in construct stiffness with the 8-hook pattern. Changing both the rods and hooks caused the stiffness to increase 44%. 27 degrees

MODEL

Changing the hook number from 8 to 12 caused a 20% increase in construct stiffness with the 6.5-mm rod. Changing the rod diameter from 5.5 to 6.35 mm caused a 29% increase in construct stiffness with the 12-hook pattern. Changing both the rods and hooks caused the construct stiffness to increase 26%. 53 degrees

MODEL

Changing the hook number from 8 to 12 caused a 14% increase in construct stiffness with the 6.35-mm rod. Changing the rod diameter from 5.5 to 6.35 mm caused a 17% (P<0.0005) increase in construct stiffness with the 12-hookpattern. Changing both rods and hooks caused the stiffness to increase 21%. Summary data on angular kyphosis: Using the same rod diameter and the same number of hooks, and progressing from a straight alignment to 27 degrees of sagittal contour decreased construct stiffness 32%. Going from straight alignment to 53 degrees decreased the stiffness 59.6%. All reported values were statistically significant (P < 0.0005).

CONCLUSIONS

The biomechanical stiffness of the straight spine was sensitive to both an increase in hook fixation sites and an increase in rod diameter. The kyphotic spines, however, were more sensitive to variations in rod diameter. Although with increasing kyphosis, the optimum instrumentation strategy will maximize both rod diameter and the number of hook sites, instrumented kyphotic spines remain biomechanically "disadvantaged" as compared with nonkyphotic instrumented spines.

Silicon micromachining to tissue engineer branched vascular channels for liver fabrication

To date, many approaches to engineering new tissue have emerged and they have all relied on vascularization from the host to provide permanent engraftment and mass transfer of oxygen and nutrients. Although this approach has been useful in many tissues, it has not been as successful in thick, complex tissues, particularly those comprising the large vital organs such as the liver, kidney, and heart. In this study, we report preliminary results using micromachining technologies on silicon and Pyrex surfaces to generate complete vascular systems that may be integrated with engineered tissue before implantation. Using standard photolithography techniques, trench patterns reminiscent of branched architecture of vascular and capillary networks were etched onto silicon and Pyrex surfaces to serve as templates. Hepatocytes and endothelial cells were cultured and subsequently lifted as single-cell monolayers from these two-dimensional molds. Both cell types were viable and proliferative on these surfaces. In addition, hepatocytes maintained albumin production. The lifted monolayers were then folded into compact three-dimensional tissues. Thus, with the use microfabrication technology in tissue engineering, it now seems feasible to consider lifting endothelial cells as branched vascular networks from two-dimensional templates that may ultimately be combined with layers of parenchymal tissue, such as hepatocytes, to form three-dimensional conformations of living vascularized tissue for implantation.

Factors associated with breast implant rupture: pilot of a retrospective analysis

This pilot study's goal was to test the feasibility of a data collection form which will be used in a scale-up study analyzing multiple surgeons' records. The goal of this expanded study will be to develop identifying factors for women who are at greater risk for having ruptured implants and, if necessary, target them for screening, surveillance, or intervention. In the pilot study, we compared factors associated with implant rupture in women with and without rupture. Similar studies have considered one or a few factors at a time and, generally, have given little attention to implant generation. We developed a data collection form after reviewing records of three surgeons. A total of 92 records was collected and analyzed. An important feature in the pilot was to compare the results of patients whose implants the surgeons had both implanted and explanted (n = 34) with those of patients whose implants the surgeons had only explanted (n = 55) (unknown = 3). This comparison could show if including all explantation patients in a surgeon's practice would bias the sample; however, based on this pilot data, concerns regarding this type of bias seem to be minimal. Similar amounts of data (e.g., implant information, history of capsular contracture, etc.) were collectable on patients whose surgeons both implanted and explanted them (87%) and who had different surgeons for implantation and explantation (84%). Though the data from this limited sample cannot offer firm conclusions on rupture associations, a few factors stood out: size of implants (38. 3% of ruptured versus 15.9% of intact implants were 100-200 cm3), history of mammography (46.8% of ruptured versus 24.4% of intact had mammograms, which is likely due to older women with older implants having more mammograms), and history of closed capsulotomy (85.1% of ruptured versus 68.9% of intact). Interestingly, additional procedures performed on the breast (e.g., scar revision, wound repair, etc.) did not affect rupture: both the ruptured and the intact groups had an average of 1.7 procedures performed. The data collection form tested very well in this pilot study. Also, including all patients in the study sample, instead of excluding those who received their implants elsewhere, did not change the results. Though there are not enough data to draw any firm conclusions regarding rupture factors, the collection instrument was rigorously tested and should perform well in an expanded study.

A review of the literature on the etiology of capsular contracture and a pilot study to determine the outcome of capsular contracture interventions

The etiology of capsular contracture is unclear and probably multifactorial. This review covers the literature on several proposed contracture factors, including filler material, implant placement, surface texture, and bacterial infection. The pilot study's goal was to test the feasibility of a data collection form, which could be used in a scaled-up study analyzing multiple surgeon's records. The goal of the expanded version of this study will be to determine the efficacy of available interventions for capsular contracture, including surveillance. The Breast Implant Public Health Project, LLC (BIPHP), piloted a retrospective review of outcomes in women who had interventions to relieve capsular contracture or had chosen a wait-and-watch approach. An evaluation of the efficacy of various treatments can help women decide if they want to pursue treatment at all and, if so, which treatment might offer them the best solution. BIPHP researchers (E.E.A., M.E.) developed a data collection form after reviewing records of three surgeons (B.C., W.P., V.L.Y.). During the data collection using the same records, we tested a randomization process to identify women with capsular contracture who underwent various interventions, including a wait-and-watch strategy, and those who had no mention of any intervention or waiting approach. Data were gathered on a total of 90 breasts with capsular contracture (scored Baker I-IV or qualitatively), of which 45 underwent a total of 102 interventions for capsular contracture. Interventions were classified as "closed capsulotomy," "surgical," or "watchful waiting." Closed capsulotomy was performed most often (47%), followed by surgery (29%) and watchful waiting (21%). Presurgical Baker scores averaged higher in breasts that underwent surgery (3.1) than for watchful waiting (2.5) or closed capsulotomy (2.3). Though closed capsulotomies had 100% of outcomes scoring "improved" or "same," 58% of the breasts underwent the procedure more than once, suggesting that the favorable outcome was short-lived. The wait-and-watch approach resulted in scores of either "same" or "worse"; surgery (open capsulotomy, repositioning, or capsulectomy) resulted in 79% improved, 16% same, and 5% worse outcomes in breasts with outcomes listed. In all intervention procedure categories, outcomes were frequently unavailable; they were noted only 60% of the time (52/87). The missing 40% may have resulted from the doctor's failure to note it in the chart, satisfied patients not returning for additional treatment, or dissatisfied patients seeking treatment elsewhere. Generally, the data collection forms and procedures were workable; however, we uncovered issues to address in the scale-up of this pilot study: (1) the outcome report rate was 60%; (2) though Baker scores are commonly used to evaluate the degree of capsular contracture, it seems that grade I may have different meanings for different surgeons, which would need to be clarified; (3) participating surgeons will need to divulge standard-of-care items that they may not have included in medical records, but routinely performed (e.g., patient massage, use of prophylactic antibiotics); and (4) records were initially separated by "implant," then researchers realized that a more useful collection would be by "breast." The latter approach captures the history of the breast in one record, which may be more important to contracture than the differences in implants. With the modifications discussed, the study can be scaled up to encompass as many records as necessary to achieve robust statistical power. These data will add to the existing literature regarding factors associated with capsular contracture and identify factors that affect the successful outcome of capsular contracture interventions.

8-methyl-pyridoxatin: A novel N-hydroxy pyridone from fungus OS-F61800 that induces erythropoietin in human cells

In the course of screening for small-molecule modulators of erythropoietin gene expression, a novel N-hydroxy pyridone was isolated from a culture of OS-F61800. Its structure was elucidated by extensive 1H and 13C NMR spectroscopic and chemical studies. This compound induced erythropoietin gene expression fivefold at a concentration of 0.3 microM, which is about threefold greater potency than our previously identified erythropoietin inducers.

Lack of long-term effects of in utero exposure to zidovudine among uninfected children born to HIV-infected women. Pediatric AIDS Clinical Trials Group Protocol 219/076 Teams

CONTEXT

With the success of zidovudine chemoprophylaxis for prevention of perinatal transmission of the human immunodeficiency virus (HIV), an increasing number of HIV-exposed but uninfected children will have in utero exposure to zidovudine and other antiretroviral drugs.

OBJECTIVE

To evaluate the long-term effects of in utero exposure to zidovudine vs placebo among a randomized cohort of uninfected children.

DESIGN

Prospective cohort study based on data collected during Pediatric AIDS Clinical Trials Group Protocol 076, a perinatal zidovudine HIV prevention trial, and Protocol 219, a long-term observational protocol.

SETTING

Pediatric research clinics in the United States.

PATIENTS

Two hundred thirty-four uninfected children born to 230 HIV-infected women enrolled in Protocol 076 and followed up through February 28, 1997, in Protocol 219 (122 in the zidovudine group and 112 in the placebo group).

MAIN OUTCOME MEASURES

Physical growth measurements, immunologic parameters, cognitive/developmental function, occurrence of neoplasms, and mortality data assessed every 6 months for children younger than 24 months and yearly thereafter or as clinically indicated. Baseline echocardiogram and funduscopic evaluations were collected before 36 months of age.

RESULTS

Median age of children at time of last follow-up visit was 4.2 years (range, 3.2-5.6 years). There were no significant differences between children exposed to zidovudine and those who received placebo in terms of sequential data on lymphocyte subsets; weight, height, and head circumference z scores; and cognitive/developmental function. No deaths or malignancies occurred. Two children (both exposed to zidovudine) are being followed up for abnormal, unexplained ophthalmic findings. One child exposed to zidovudine had a mild cardiomyopathy on echocardiogram at the age of 48 months; the child is clinically asymptomatic.

CONCLUSIONS

No adverse effects were observed in HIV-uninfected children with in utero and neonatal exposure to zidovudine followed up for as long as 5.6 years. Continued prospective evaluations of children born to HIV-infected women who are exposed to antiretroviral or immunotherapeutic agents are critical to assess the long-term safety of interventions that prevent perinatal HIV transmission.

The concentrations of clinafloxacin in alveolar macrophages, epithelial lining fluid, bronchial mucosa and serum after administration of single 200 mg oral doses to patients undergoing fibre-optic bronchoscopy

The concentrations of clinafloxacin were measured in serum, bronchial mucosa, alveolar macrophages and epithelial lining fluid after single 200 mg oral doses of clinafloxacin had been administered to 15 subjects who were undergoing bronchoscopy. Concentrations were measured using a microbiological assay method. Mean concentrations in serum, bronchial mucosa, alveolar macrophages and epithelial lining fluid at a mean of 1.27 h post-dose were 1.54, 2.65, 15.60 and 2.71 mg/L respectively. These site concentrations exceeded the MIC90 for common respiratory pathogens and indicate that clinafloxacin is likely to be effective in the treatment of a wide range of respiratory tract infections.

Epolones: novel sesquiterpene-tropolones from fungus OS-F69284 that induce erythropoietin in human cells

In the course of our screening for small molecule modulators of erythropoietin gene expression, two novel sesquiterpene tropolones and pycnidone were isolated from a culture of OS-F69284 (ATCC 74390). Their structures were elucidated by extensive 1H and 13C NMR spectroscopic studies and chemical reactions. These compounds induced erythropoietin gene expression 5-fold at a concentration of 1-1.6 microM.

Requirements for binding and signaling of the kinase domain receptor for vascular endothelial growth factor

Vascular endothelial growth factor (VEGF) is a dimeric hormone that controls much of vascular development through binding and activation of its kinase domain receptor (KDR). We produced analogs of VEGF that show it has two receptor-binding sites which are located near the poles of the dimer and straddle the interface between subunits. Deletion experiments in KDR indicate that of the seven IgG-like domains in the extracellular domain, only domains 2-3 are needed for tight binding of VEGF. Monomeric forms of the extracellular domain of KDR bind approximately 100 times weaker than dimeric forms showing a strong avidity component for binding of VEGF to predimerized forms of the receptor. Based upon these structure-function studies and a mechanism in which receptor dimerization is critical for signaling, we constructed a receptor antagonist in the form of a heterodimer of VEGF that contained one functional and one non-functional site. These studies establish a functional foundation for the design of VEGF analogs, mimics, and antagonists.

Concentrations of levofloxacin (HR 355) in the respiratory tract following a single oral dose in patients undergoing fibre-optic bronchoscopy

Concentrations of levofloxacin were measured in bronchial biopsies, alveolar macrophages (AM), epithelial lining fluid (ELF) and serum following a single oral dose. Concentrations were measured by a microbiological assay method. A total of 35 patients undergoing fibre-optic bronchoscopy were studied. Mean serum, AM, ELF and biopsy concentrations were as follows. 0.5 h: 4.73 mg/L, 19.1 mg/L, 4.74 mg/L and 4.3 mg/kg; 1 h: 6.6 mg/L, 32.5 mg/L, 10.8 mg/L and 8.3 mg/kg; 2 h: 4.9 mg/L, 41.9 mg/L, 9.0 mg/L and 6.5 mg/kg; 4 h: 4.1 mg/L, 27.7 mg/L, 10.9 mg/L and 6.0 mg/kg; and 6-8 h: 4.0 mg/L, 38.4 mg/L, 9.6 mg/L and 4.0 mg/kg respectively. Mean serum and AM concentrations at 12-24 h were 1.2 and 13.9 mg/L respectively (concentrations in biopsy and ELF were only measurable in three of the six patients). These concentrations exceed the MIC90s of the common respiratory pathogens, Haemophilus influenzae (0.015 mg/L), Moraxella catarrhalis (0.06 mg/L) and Streptococcus pneumoniae (1 mg/L) and suggest that levofloxacin should be efficacious in the treatment of community- and hospital-acquired respiratory infection.

Ruptured or intact: what can linear echoes within silicone breast implants tell us?

OBJECTIVE

During sonographic evaluation of silicone breast implants for possible rupture, we have frequently encountered several patterns of linear echoes within the implants. To our knowledge, the significance of this finding has not been established in the literature. The purpose of this study was to determine whether internal echoes are significant in predicting implant rupture.

SUBJECTS AND METHODS

Thirty-three patients with 64 silicone implants were prospectively entered into a study that included gray-scale sonography of the implants and subsequent surgical removal. Echo patterns within the implants were retrospectively evaluated on hard-copy films and compared with the integrity of the implant at surgery.

RESULTS

Three categories of internal echo patterns were identified: "thick linear echoes." "thin linear echoes," and "commas." One or more of these echo patterns were seen in 57 (89%) of the 64 implants. Thick linear echoes were seen in 23 (36%) of the 64 implants, thin linear echoes were seen in 33 (52%) of the 64 implants, and commas were seen in 47 (73%) of the 64 implants. All echo patterns were seen in intact and ruptured implants with nearly equal frequency. We found no statistical significance for any echo pattern in predicting whether an implant was ruptured or intact. Of the 64 implants, four were entirely free of internal echoes. All four implants were intact.

CONCLUSION

A variety of linear echoes can be seen in most silicone breast implants on gray-scale sonography. The presence or absence of linear echoes is not useful in predicting implant rupture. Complete absence of internal echoes, while highly predictive of an intact implant, is infrequently seen.

Concentrations of trovafloxacin in bronchial mucosa, epithelial lining fluid, alveolar macrophages and serum after administration of single or multiple oral doses to patients undergoing fibre-optic bronchoscopy

Concentrations of trovafloxacin were measured in serum, alveolar macrophages, epithelial lining fluid and bronchial mucosa following single and multiple oral doses. Concentrations were determined using a microbiological assay method. There were 18 subjects in the single dose and nine subjects in the multiple dose groups. After single dosing, mean concentrations in serum, alveolar macrophages, epithelial lining fluid and bronchial mucosa at 6, 12 and 24 h were as follows: 6 h, 1.41 mg/L, 19.06 mg/L, 3.01 mg/L and 1.52 mg/kg; 12 h, 0.85 mg/L, 16.22 mg/L, 4.8 mg/L and 1.01 mg/kg; 24 h, 0.37 mg/L, 10.23 mg/L, 0.93 mg/L, and no measurable concentration, respectively. After multiple dosing (approximately 6 h post-dose) the corresponding concentrations were 1.47 mg/L, 34.3 mg/L, 10.21 mg/L and 1.67 mg/kg, respectively. These concentrations exceed the MIC90s for the common respiratory pathogens, Haemophilus influenzae 0.06 mg/L, Moraxella catarrhalis 0.008 mg/L and Streptococcus pneumoniae 0.12 mg/L and suggest that trovafloxacin should be efficacious in the treatment of community- and hospital-acquired respiratory infections.

The Bentham Unit: a pilot remand and assessment service for male mentally disordered remand prisoners. II: Report of an independent evaluation

BACKGROUND

Findings are presented from an evaluation of a pilot remand and assessment service--the Bentham Unit. The aims of the Bentham Unit are to provide rapid assessment, identify mentally disordered remand prisoners, and speed their transfer from prison to NHS care, where a need is indicated.

METHOD

The number, rate and speed of referral, assessment and transfer to NHS care of offenders remanded to Wormwood Scrubs prison during periods before and after the Bentham Unit opened were compared.

RESULTS

The service attracted a large volume of referrals. Between the two periods, significant increases in the numbers of referrals and hospital disposals, and major reductions in the interval between reception on remand into the prison, NHS assessment and transfer to NHS care, were observed.

CONCLUSIONS

The aims of the unit were met. Implications for service configurations are discussed.

Oxygen protocols for the prevention of hypoxemia. A review for case managers

Case managers are challenged by the need to ensure quality care for patients in the face of increasing demands on the health care system to provide more economic care. These economic pressures often cause hospitalized patients to be transferred from critical care areas earlier than in years past. As a result, hypoxemia-inadequate oxygenation of the blood-is emerging as a serious patient safety problem in noncritical care areas of the hospital. The medical literature recently has begun to document hypoxemia in some patient groups on the general care floor, where continuous monitoring of patients' respiratory status usually is no longer employed. The serious health consequences of hypoxemia, the fact that it can affect nearly any hospitalized patient, and the potentially high cost of treating hypoxemia-related morbidity are drawing the attention of the medical community. Case managers are in a position to address this emerging problem by working with hospitals and health care institutions to identify at-risk patients and develop strategies to improve both clinical and financial outcomes. Patient care protocols are one effective strategy to standardize monitoring of patients deemed to be at risk. Early detection and treatment of hypoxemia have the potential to improve patient care while significantly reducing medical costs.

A biomechanical study of the flexor digitorum superficialis: effects of digital pulley excision and loss of the flexor digitorum profundus

Many reports have been devoted to characterizing the significance of the pulleys for the flexor digitorum profundus (FDP). However, no comparable work has been published on the flexor digitorum superficialis (FDS). This study characterized the FDS in a human cadaver model. Eleven fresh-frozen cadaver hands were used. By using a tensiometer, data were gathered for tendon excursion, tendon load, and work of flexion. Changes in efficiency were caused by excision of annular pulleys A1, A2, A3, and the palmar aponeurotic pulley. We also measured the effect of FDP excision on FDS efficiency. Sectioning of the A2 and A3 pulleys together caused statistically significant losses of efficiency in all three parameters (work, load, and excursion). When the FDP was removed from a finger with an intact pulley system, losses in both work and excursion efficiencies were significant. Removing the FDP while cutting different pulleys caused significant decrease in FDS excursion efficiency. We conclude that A2 and A3 are the most important pulleys for maintaining normal FDS function, and that the presence of the FDP in the digital sheath is essential for optimal FDS excursion efficiency.

Novel analog of atrial natriuretic peptide selective for receptor-A produces increased diuresis and natriuresis in rats

Atrial natriuretic peptide (ANP) binds to natriuretic peptide receptor-A (NPR-A), a membrane guanylyl cyclase, and to natriuretic peptide receptor-C (NPR-C), which plays a role in peptide clearance. Rat ANP (rANP) mutants that bind rat NPR-A selectively over rat NPR-C were isolated from randomized libraries of rANP-display phage by differential panning. One variant was identified with reduced NPR-C binding; rANP (G16R, A17E, Q18A) [rANP(REA18)]. Synthetic rANP(REA18) was equipotent with rANP in stimulating cGMP production from cloned rat NPR-A (ED50 = 1.8 nM) and was reduced in NPR-C binding by approximately 200-fold. When infused into conscious rats at 0.325 microg/min for 30 min rANP elicited an identical decrease in blood pressure compared with 0.25 microg/min of rANP(REA18), however the natriuretic (P < 0.05) and diuretic (P = 0.07) responses to rANP(REA18) were greater. These data are consistent with a role for NPR-C as a local decoy receptor attenuating NPR-A effects in the kidney, where these receptors are coexpressed. Improved NPR-A specificity could provide more effective natriuretic peptides for treatment of acute renal failure or heart failure.

The use of capillary electrophoresis to monitor the stability of a dual-action cephalosporin in solution

Ro 23-9424 is a broad-spectrum antibacterial agent consisting of a cephalosporin and a quinolone moiety which are held together by an ester linkage. This compound has limited solubility in water but is more soluble at alkaline pH. Such high pH values, however, lead to stability problems due to the lability of the ester linkage, and result in the formation of the free quinolone and cephalosporin moieties. The balance between solubility and stability presents a challenge in formulation development for this compound. Thus, it is important to effectively monitor the stability of Ro 23-9424 after it has been reconstituted in different solvent systems. In this manner, a diluent which does not lead to degradation of the drug can be identified. A capillary electrophoresis method was developed and validated to monitor the stability of Ro 23-9424. The method was found to meet acceptable criteria for method precision, system precision, linearity and limits of detection and quantitation. The method was used to monitor the stability and measure the half-life of Ro 23-9424 in water and in an L-arginine-sodium benzoate-saline diluent designed to mimic the drug delivery system. This work shows that capillary electrophoresis can be used to compare the stability of a drug in different solutions as an aid in formulation development.

Stability of reamed and unreamed intramedullary tibial nails: a biomechanical study

We examined the correlation of bone mineral density and bone strength in the cadaver tibia, and looked in vitro at the relative stability of tibial fractures fixed with either reamed or unreamed tibial nails. Bone-mineral density correlated well with bone strength (r = 0.946), but paired tibias did not correlate closely. The unreamed nail-bone construct was less stable than the reamed construct in each pair tested (P < 0.05), and a comparison of all bones showed it to be less stable at all levels of our testing regimen, including failure (P < 0.01). Bending and breakage was seen in four of the smaller unreamed interlocking screws (4 mm).

Diagnosis of breast implant rupture: imaging findings and relative efficacies of imaging techniques

OBJECTIVE

The purpose of this study was to compare the efficacies of mammography, sonography, CT, and MR imaging in the detection of breast implant rupture and to analyze the imaging findings.

SUBJECTS AND METHODS

Thirty-two women with 63 silicone breast implants participated in the study. All but one had signs and symptoms suggestive of rupture, and all had requested that their implants be removed before they were enrolled in this imaging study. All patients had film-screen mammography, sonography, CT, and MR imaging. Twenty-two ruptures were found at surgery; 21 were intracapsular and one was extracapsular. The relative efficacies of the imaging studies were determined, and the imaging findings were compared with the surgical results.

RESULTS

Of the 32 women with 63 implants, mammographic sensitivity for detecting implant rupture was only 23% but the specificity was 98%. Sonography had a higher sensitivity (59%), but its specificity was significantly lower (79%). CT had a sensitivity of 82% and a specificity of 88%. MR was the only imaging technique that consistently provided evidence that enabled the evaluation of intracapsular and extracapsular ruptures. The sensitivity and specificity of MR imaging were 95% and 93%, respectively.

CONCLUSION

Our results show that MR imaging is more sensitive and specific for the detection of breast implant rupture than is mammography, CT, or sonography.

Recognition by HLA-A2-restricted cytotoxic T lymphocytes of endogenously generated and exogenously provided synthetic peptide analogues of the influenza A virus matrix protein

Experiments were carried out to determine whether complexes between MHC class I molecules and synthetic peptides are representative of those formed under more physiologically relevant conditions, with peptides derived intracellularly from processed antigens. Lysis of cells sensitized with exogenously provided and endogenously generated peptide analogues of the optimal nonameric peptide 58-66 (GILGFVFTL; derived from the influenza virus matrix protein) was compared. Endogenous loading was accomplished by expressing minigene DNA coding for alanine-substituted analogues of peptide 58-66 in HLA-A2-positive cells. Susceptibility to lysis by HLA-A2-restricted, peptide-specific cytotoxic lymphocytes was compared with lysis of cells sensitized with the same synthetic peptides. Although results were quite comparable, differences were observed. The endogenously presented analogues 58-66L60A, G61A, T65A, and L66A were recognized more efficiently than the corresponding exogenously presented analogues. This difference in recognition was most striking for peptide 58-66G61A. These results indicate the need for caution in using synthetic peptides in defining peptide binding motifs. Additional experiments with endogenously expressed analogues of 58-66 with substitutions other than alanine were carried out to define the interaction between this peptide and HLA-A2. Results are compatible with the interpretation that residues 58, 59, and 60 interact with pockets A, B, and D, respectively, in the HLA-A2 binding groove and that these interactions contribute to peptide binding.

Sequence motifs important for peptide binding to the human MHC class I molecule, HLA-A2

Previous studies have indicated that most HLA-A2-binding peptides are 9 amino acid (aa) residues long, with a Leu at position 2 (P2), and a Val or Leu at P9. We compared the binding properties of different peptides by measuring the rate of dissociation of beta 2-microglobulin from peptide-specific HLA-A2 complexes. The simplest peptide that we identified that could form HLA-A2 complexes had the sequence (in single letter aa code) GLFGGGGGV, indicating that three nonglycine aa are sufficient for binding to HLA-A2. To determine whether most nonapeptides that contained Leu at P2 and Val or Leu at P9 could bind to HLA-A2, we tested the binding of nonapeptides selected from published HIV and melanoma protein sequences, and found that six of seven tested formed stable HLA-A2 complexes. We identified an optimal antigenic undecapeptide from the cytomegalovirus gB protein that could form stable HLA-A2 complexes that contained apparent anchor residues at P2 and P11 (sequence FIAGN-SAYEYV), indicating that the spacing between anchor residues can be somewhat variable. Finally, we tested the importance of every aa in the influenza A matrix peptide 58-66 (sequence GILGFVFTL) for binding to HLA-A2, by using Ala-substituted and Lys-substituted peptides. We found that multiple positions were important for stable binding, including P2, P3, P5-P7, and P9. We conclude that the P2 and P9 anchor residues are of prime importance for peptide binding to HLA-A2. However, other peptide side chains (especially at P3) contribute to the stability of the interaction. In certain cases, the optimal length for peptide binding can be longer than 9 residues.

Sequence motifs important for peptide binding to the human MHC class I molecule, HLA-A2

Previous studies have indicated that most HLA-A2-binding peptides are 9 amino acid (aa) residues long, with a Leu at position 2 (P2), and a Val or Leu at P9. We compared the binding properties of different peptides by measuring the rate of dissociation of beta 2-microglobulin from peptide-specific HLA-A2 complexes. The simplest peptide that we identified that could form HLA-A2 complexes had the sequence (in single letter aa code) GLFGGGGGV, indicating that three nonglycine aa are sufficient for binding to HLA-A2. To determine whether most nonapeptides that contained Leu at P2 and Val or Leu at P9 could bind to HLA-A2, we tested the binding of nonapeptides selected from published HIV and melanoma protein sequences, and found that six of seven tested formed stable HLA-A2 complexes. We identified an optimal antigenic undecapeptide from the cytomegalovirus gB protein that could form stable HLA-A2 complexes that contained apparent anchor residues at P2 and P11 (sequence FIAGN-SAYEYV), indicating that the spacing between anchor residues can be somewhat variable. Finally, we tested the importance of every aa in the influenza A matrix peptide 58-66 (sequence GILGFVFTL) for binding to HLA-A2, by using Ala-substituted and Lys-substituted peptides. We found that multiple positions were important for stable binding, including P2, P3, P5-P7, and P9. We conclude that the P2 and P9 anchor residues are of prime importance for peptide binding to HLA-A2. However, other peptide side chains (especially at P3) contribute to the stability of the interaction. In certain cases, the optimal length for peptide binding can be longer than 9 residues.