Modulating Macrophage Clearance of Nanoparticles: Comparison of Small-Molecule and Biologic Drugs as Pharmacokinetic Modifiers of Soft Nanomaterials

Nanomedicines show benefits in overcoming the limitations of conventional drug delivery systems by reducing side effects, toxicity, and exhibiting enhanced pharmacokinetic (PK) profiles to improve the therapeutic window of small-molecule drugs. However, upon administration, many nanoparticles (NPs) prompt induction of host innate immune responses, which in combination with other clearance pathways such as renal and hepatic, eliminate up to 99% of the administered dose. Here, we explore a drug predosing strategy to transiently suppress the mononuclear phagocyte system (MPS), subsequently improving the PK profile and biological behaviors exhibited by a model NP system [hyperbranched polymers (HBPs)] in an immunocompetent mouse model. In vitro assays allowed the identification of five drug candidates that attenuated cellular association. Predosing of lead compounds chloroquine (CQ) and zoledronic acid (ZA) further showed increased HBP retention within the circulatory system of mice, as shown by both fluorescence imaging and positron emission tomography-computed tomography. Flow cytometric evaluation of spleen and liver tissue cells following intravenous administration further demonstrated that CQ and ZA significantly reduced HBP association with myeloid cells by 23 and 16%, respectively. The results of this study support the use of CQ to pharmacologically suppress the MPS to improve NP PKs.

Exploring current undergraduate student perspectives on the introduction of the degree apprenticeship scheme in diagnostic radiography - a single institution study

INTRODUCTION

The first degree apprenticeship programme in diagnostic radiography was launched in March 2020. This route into radiography runs in parallel with 'conventional' pre-registration programmes where students apply to a higher education institution (HEI) and undertake discrete clinical placements. The aim of this study was to explore the perspectives of pre-registration students on the diagnostic radiographer degree apprenticeship route.

METHODS

A qualitative approach (online questionnaire) gathered attitudes and opinions of pre-registration students from a single HEI, regarding the degree apprenticeship programme. Participants were pre-registration medical imaging students from all stages of the programme (n = 204). Braun and Clarks's thematic analysis was employed for data analysis.

RESULTS

A response rate of 21% (n = 44) was recorded. Four themes emerged from data analysis: (1) misunderstandings surrounding the degree apprenticeship, (2) financial implications and (3) practical experience associated with both degree courses and (4) the experience the pre-registration degree has to offer.

CONCLUSION

There was an apparent lack of understanding regarding the degree apprenticeship leading students to misinterpret aspects of the course. Additionally, students highlighted the earning aspect of the apprenticeship to be an advantage in comparison to student debts associated with the traditional pre-registration programmes. Furthermore, students emphasised the advantage of the clinical focus practice associated with the degree apprenticeship. Nevertheless, students who have selected the HEI route still value what the traditional pre-registration degree offers.

IMPLICATIONS FOR PRACTICE

As degree apprenticeship programmes become widely available, a greater awareness should, therefore, follow. In the interim, there is scope for HEIs to seek to raise awareness of degree apprenticeship provision. HEIs should seek to allay any concerns and highlight the benefits of having this alternative route into the profession.

Nanoparticle based medicines: approaches for evading and manipulating the mononuclear phagocyte system and potential for clinical translation

For decades, nanomedicines have been reported as a potential means to overcome the limitations of conventional drug delivery systems by reducing side effects, toxicity and the non-ideal pharmacokinetic behaviour typically exhibited by small molecule drugs. However, upon administration many nanoparticles prompt induction of host inflammatory responses due to recognition and uptake by macrophages, eliminating up to 95% of the administered dose. While significant advances in nanoparticle engineering and consequent therapeutic efficacy have been made, it is becoming clear that nanoparticle recognition by the mononuclear phagocyte system (MPS) poses an impassable junction in the current framework of nanoparticle development. Hence, this has negative consequences on the clinical translation of nanotechnology with respect to therapeutic efficacy, systemic toxicity and economic benefit. In order to improve the translation of nanomedicines from bench-to-bedside, there is a requirement to either modify nanomedicines in terms of how they interact with intrinsic processes in the body, or modulate the body to be more accommodating for nanomedicine treatments. Here we provide an overview of the current standard for design elements of nanoparticles, as well as factors to consider when producing nanomedicines that have minimal MPS-nanoparticle interactions; we explore this landscape across the cellular to tissue and organ levels. Further, rather than designing materials to suit the body, a growing research niche involves modulating biological responses to administered nanomaterials. We here discuss how developing strategic methods of MPS 'pre-conditioning' with small molecule or biological drugs, as well as implementing strategic dosing regimens, such as 'decoy' nanoparticles, is essential to increasing nanoparticle therapeutic efficacy. By adopting such a perspective, we hope to highlight the increasing trends in research dedicated to improving nanomedicine translation, and subsequently making a positive clinical impact.

Hemispheric asymmetry in ocean change and the productivity of ecosystem sentinels

Climate change and other human activities are causing profound effects on marine ecosystem productivity. We show that the breeding success of seabirds is tracking hemispheric differences in ocean warming and human impacts, with the strongest effects on fish-eating, surface-foraging species in the north. Hemispheric asymmetry suggests the need for ocean management at hemispheric scales. For the north, tactical, climate-based recovery plans for forage fish resources are needed to recover seabird breeding productivity. In the south, lower-magnitude change in seabird productivity presents opportunities for strategic management approaches such as large marine protected areas to sustain food webs and maintain predator productivity. Global monitoring of seabird productivity enables the detection of ecosystem change in remote regions and contributes to our understanding of marine climate impacts on ecosystems.

X-ray power and yield measurements at the refurbished Z machine

Advancements have been made in the diagnostic techniques to measure accurately the total radiated x-ray yield and power from z-pinch implosion experiments at the Z machine with high accuracy. The Z machine is capable of outputting 2 MJ and 330 TW of x-ray yield and power, and accurately measuring these quantities is imperative. We will describe work over the past several years which include the development of new diagnostics, improvements to existing diagnostics, and implementation of automated data analysis routines. A set of experiments on the Z machine were conducted in which the load and machine configuration were held constant. During this shot series, it was observed that the total z-pinch x-ray emission power determined from the two common techniques for inferring the x-ray power, a Kimfol filtered x-ray diode diagnostic and the total power and energy diagnostic, gave 449 TW and 323 TW, respectively. Our analysis shows the latter to be the more accurate interpretation. More broadly, the comparison demonstrates the necessity to consider spectral response and field of view when inferring x-ray powers from z-pinch sources.

A preliminary comparison of total skin electron treatment techniques to demonstrate the application of a mid-torso phantom for measurement of dose penetration

OBJECTIVES

In the UK, the treatment of patients with mycosis fungoides using total skin electron (TSE) beam therapy is undertaken using a number of different irradiation techniques. As part of a review of these techniques, a comparative set of measurements would be useful to determine how the techniques differ in terms of dose distribution. A dose penetration intercomparison method that could be used as part of such a study is presented here.

METHODS

The dose penetrations for six treatment techniques currently or recently used in four centres in the UK were measured. The variation of dose with skin depth was measured in a WT1 solid water mid-torso phantom. The phantom is portable and suitable to be used in all the techniques. It is designed to hold four small radiochromic film dosemeters to investigate the variation in dose around the mid-torso. For each treatment technique, the phantom was irradiated using the clinical set-up.

RESULTS

The phantom performed well and was able to measure dose penetration and the uniformity of penetration for several treatment techniques.

CONCLUSION

These preliminary results demonstrate that there is some variation in dose distribution between different TSE treatment techniques and that the phantom could be used in a more comprehensive intercomparison. The results are not intended to demonstrate comprehensively the range of penetration that can be achieved in clinical practice as, for one of the treatment techniques, the penetration is customised for the extent of the disease.

Perinatal predictors of outcome in gastroschisis

OBJECTIVE

To identify perinatal risk variables predictive of outcome in gastroschisis.

STUDY DESIGN

Gastroschisis cases were collected over a 3-year period from a national database. Risk variables evaluated included gestational age (GA), birth weight, time of birth, admission illness severity (score for neonatal acute physiology-II, SNAP-II) score, and abdominal closure type. Mortality and survival outcomes were analyzed. Multivariate analyses were performed.

RESULT

In all, 239 infants were survived (96%). SNAP-II score predicted mortality (relative risk (RR)=1.07, 95% confidence interval (CI)=1.0 to 1.1). Length of hospital stay (LOS) and ventilation days were predicted by GA and by SNAP-II score. SNAP-II score predicted total parenteral nutrition (TPN) days (P=0.006). Severe cholestasis (conjugated bilirubin of >10 mg per 100 ml) was inversely related to GA (RR=0.77, 95% CI=0.61 to 0.97) and directly to categorical SNAP-II score (RR=3.4, 95% CI=1.2 to 10.1). Urgent closure predicted fewer TPN days (P=0.003) and shorter LOS (P=0.0002).

CONCLUSION

SNAP-II scores significantly predict mortality and survival outcomes. Urgent closure favors fewer TPN days and shorter LOS. Our data refute routine preterm delivery in gastroschisis.

Indirect genetic effects in a sex-limited trait: the case of breeding time in red-billed gulls

Female reproductive performance can be strongly affected by male care, so that breeding time, a trait expressed only by females, can be seen as one trait determined by both male and female genotypes. Animal model analyses of a 46-year study of red-billed gulls (Larus novaehollandiae scopulinus) revealed that laying date was not heritable in females (h(2) = 0.001 +/- 0.030), but significantly so in males (h(2) = 0.134 +/- 0.029). Heritability of breeding time in males probably reflects genetic variability in some other trait such as courtship feeding ability. In line with predictions of evolutionary models incorporating indirect genetic effects, the strong and consistent directional selection for advanced breeding time has not resulted in detectable selection response in males. Our results demonstrate that a female trait is largely determined by genetic characteristics of its mate, and hence, any evolutionary change in red-billed gull breeding time depends critically on genetic variation in males.

Climate change and evolution: disentangling environmental and genetic responses

Rapid climate change is likely to impose strong selection pressures on traits important for fitness, and therefore, microevolution in response to climate-mediated selection is potentially an important mechanism mitigating negative consequences of climate change. We reviewed the empirical evidence for recent microevolutionary responses to climate change in longitudinal studies emphasizing the following three perspectives emerging from the published data. First, although signatures of climate change are clearly visible in many ecological processes, similar examples of microevolutionary responses in literature are in fact very rare. Second, the quality of evidence for microevolutionary responses to climate change is far from satisfactory as the documented responses are often - if not typically - based on nongenetic data. We reinforce the view that it is as important to make the distinction between genetic (evolutionary) and phenotypic (includes a nongenetic, plastic component) responses clear, as it is to understand the relative roles of plasticity and genetics in adaptation to climate change. Third, in order to illustrate the difficulties and their potential ubiquity in detection of microevolution in response to natural selection, we reviewed the quantitative genetic studies on microevolutionary responses to natural selection in the context of long-term studies of vertebrates. The available evidence points to the overall conclusion that many responses perceived as adaptations to changing environmental conditions could be environmentally induced plastic responses rather than microevolutionary adaptations. Hence, clear-cut evidence indicating a significant role for evolutionary adaptation to ongoing climate warming is conspicuously scarce.

Comparison of 50 kV Facilities for Contact Radiotherapy

The radiation characteristics of a short source to surface distance (SSD) contact therapy tube in clinical use at the Centre Antoine-Lacassagne, Nice and a long SSD unit at the Clatterbridge Centre for Oncology were compared. The output from the tube at Nice had a dose rate of approximately double that of the tube at Clatterbridge, whereas the tube at Clatterbridge had a slightly higher value of the half value layer. Depth dose measurements were made with GafChromic MD55 film and SSD corrected depth dose curves showed good agreement between centres. Profiles at 2mm depth also showed comparable levels of flatness and uniformity.

Increased susceptibility to maternal aneuploidy demonstrated by comparative genomic hybridization analysis of human MII oocytes and first polar bodies

Single cell comparative genomic hybridization (CGH) was employed to extensively investigate 24 unfertilized or in vitromatured meiosis II oocytes and their corresponding first polar bodies (PBs), to determine how and whether all 23 chromosomes participate in female meiosis I errors and to accurately estimate the aneuploidy rate in the examined cells. Results were obtained for 15 oocytes and 16 PBs, representing 23 eggs (MII oocyte-PB complexes) donated from 15 patients (average age 32.2 years). Abnormalities were detected in ten eggs, giving an overall aneuploidy rate of 43.5%. In all, fourteen anomalies were scored, with the fertilized oocyte being at risk of monosomy in eight cases and at risk of trisomy in six; chromosomes of various sizes participated. CGH was able to give a comprehensive aneuploidy rate, as both absence of chromosomal material and the presence of extra copies were accurately scored. The aneuploidy mechanisms determined were: classical whole univalent non-disjunction; chromatid predivision prior to anaphase I, leading to metaphase II imbalance. There was also evidence of germinal mosaicism for a trisomic cell line. Three patients appeared to be predisposed to meiosis I errors, based on the presence of either multiple abnormalities in one or more of their examined cells, or of the same type of abnormality in all of their cells. Exclusion of these susceptible patients reduces the aneuploidy rate to 20%. Various hypotheses are put forward to explain these observations in order to stimulate research into the complex nature of female meiotic regulation.

The Effects of Buffered Propionic Acid-Based Additives Alone or Combined with Microbial Inoculation on the Fermentation of High Moisture Corn and Whole-Crop Barley

Buffered propionic acid-based additives (BP) alone or in combination with a microbial inoculant containing lactic acid bacteria (MI) were mixed with ground, high moisture corn or whole-crop barley and ensiled in triplicate laboratory silos to investigate their effects on silage fermentation and aerobic stability. The inoculant and chemicals were applied separately for treatments that included both additives. The addition of MI alone had no effect on DM recovery, fermentation end products, or aerobic stability of high moisture corn. However, treatments with 0.1 and 0.2% BP (alone and the combination) had more than 10- and 100-fold fewer yeasts, respectively, and they also had greater concentrations of propionic acid than did untreated corn. Corn treated with only 0.1 (161 h) and 0.2% (218 h) BP tended to be more stable when exposed to air than untreated corn (122 h). Treatment with MI + 0.2% BP markedly improved the aerobic stability (>400 h) of high moisture corn. With whole-crop barley, the addition of MI alone, BP alone, and combinations of MI and BP prevented the production of butyric acid that was found in untreated silage (0.48%). All barley silages that had MI in their treatments underwent a more efficient fermentation than treatments without MI, as evident by a greater ratio of lactic:acetic acid and more DM recovery than in untreated silage. Increasing levels (0.1 to 0.2%) of BP added together with MI improved the aerobic stability of barley (190 and 429 h) over the addition of MI alone (50 h). These data show that buffered propionic acid-based products are compatible with microbial inoculants and, in some circumstances when used together, they can improve the fermentation and aerobic stability of silages.

X-ray emission from z pinches at 10 7 A: current scaling, gap closure, and shot-to-shot fluctuations

We have measured the x-ray power and energy radiated by a tungsten-wire-array z pinch as a function of the peak pinch current and the width of the anode-cathode gap at the base of the pinch. The measurements were performed at 13- and 19-MA currents and 1-, 2-, 3-, and 4-mm gaps. The wire material, number of wires, wire-array diameter, wire-array length, wire-array-electrode design, normalized-pinch-current time history, implosion time, and diagnostic package were held constant for the experiments. To keep the implosion time constant, the mass of the array was increased as I2 (i.e., the diameter of each wire was increased as I), where I is the peak pinch current. At 19 MA, the mass of the 300-wire 20-mm-diam 10-mm-length array was 5.9 mg. For the configuration studied, we find that to eliminate the effects of gap closure on the radiated energy, the width of the gap must be increased approximately as I. For shots unaffected by gap closure, we find that the peak radiated x-ray power P(r) proportional to I1.24+/-0.18, the total radiated x-ray energy E(r) proportional to I1.73+/-0.18, the x-ray-power rise time tau(r) proportional to I0.39+/-0.34, and the x-ray-power pulse width tau(w) proportional to demonstrate that the internal energy and radiative opacity of the pinch are not responsible for the observed subquadratic power scaling. Heuristic wire-ablation arguments suggest that quadratic power scaling will be achieved if the implosion time tau(i) is scaled as I(-1/3). The measured 1sigma shot-to-shot fluctuations in P(r), E(r), tau(r), tau(w), and tau(i) are approximately 12%, 9%, 26%, 9%, and 2%, respectively, assuming that the fluctuations are independent of I. These variations are for one-half of the pinch. If the half observed radiates in a manner that is statistically independent of the other half, the variations are a factor of 2(1/2) less for the entire pinch. We calculate the effect that shot-to-shot fluctuations of a single pinch would have on the shot-success probability of the double-pinch inertial-confinement-fusion driver proposed by Hammer et al. [Phys. Plasmas 6, 2129 (1999)]. We find that on a given shot, the probability that two independent pinches would radiate the same peak power to within a factor of 1+/-alpha (where 0< or =alpha<<1) is equal to erf(alpha/2sigma), where sigma is the 1sigma fractional variation of the peak power radiated by a single pinch. Assuming alpha must be < or =7% to achieve adequate odd-Legendre-mode radiation symmetry for thermonuclear-fusion experiments, sigma must be <3% for the shot-success probability to be > or =90%. The observed (12/2(1/2))%=8.5% fluctuation in P(r) would provide adequate symmetry on 44% of the shots. We propose that three-dimensional radiative-magnetohydrodynamic simulations be performed to quantify the sensitivity of the x-ray emission to various initial conditions, and to determine whether an imploding z pinch is a spatiotemporal chaotic system.

Sequential FISH analysis of oocytes and polar bodies reveals aneuploidy mechanisms

OBJECTIVES

Constitutional aneuploidy occurs in at least 5% of recognised pregnancies, with apparent preferential involvement of the X chromosome and the smaller autosomes. Molecular cytogenetic investigations of cleavage-stage embryos have revealed anomalies affecting all sizes of chromosomes. The aim was to investigate the variety of anomalies arising during maternal meiosis I by analysis of unfertilised oocytes and polar bodies to gain insight into aneuploidy mechanisms.

METHODS

Sequential FISH analysis was carried out with specific probes derived from eight chromosomes, representing all sizes. Only imbalance due to a gain of a whole chromosome or chromatid, represented by extra signals, was counted to avoid artefact.

RESULTS

Data were obtained on 236 eggs from 124 patients of average age 32.5 years (range 22-44). Ten patients (average 32.6 years) had abnormal eggs. The abnormality rate for oocytes and for polar bodies was close to 4% for each. Fourteen hyperploidies were found, seven involving additional single chromatids. The abnormalities affected chromosomes 13,16,18, 21 and X but not chromosomes 1, 9 or 12.

CONCLUSION

The data provide evidence for several mechanisms leading to aneuploidy, including classical non-disjunction of whole univalents; pre-division of chromatids prior to anaphase I, leading to imbalance detected at metaphase II; gonadal mosaicism for a trisomic cell line and preferential involvement of the smaller chromosomes. Monosomy for the large autosomes is not uncommon in cleavage-stage embryos and may additionally arise from anaphase lag preferentially affecting such chromosomes.

The effect of delayed ensiling and application of a propionic acid-based additive on the fermentation of barley silage

Prolonged exposure to air can adversely affect the silage fermentation process. To investigate a possible method to overcome this problem, we determined if a buffered propionic acid-based additive, applied to chopped, whole-plant barley exposed to air before ensiling, would affect the subsequent fermentation. Wilted forage was chopped and treated with nothing, or with 0.1% (wt/wt wet forage) of a buffered propionic acid-based additive and ensiled immediately in quadruplicate 20-L laboratory silos. Portions of the chopped forage, untreated and treated, were left in loose piles in a barn for 24 h before ensiling. Another portion of the untreated silage exposed to air for 24 h was also treated with 0.1% of the additive just before ensiling. Prolonged exposure to air before ensiling increased the numbers of yeasts on forages by more than 1,000-fold. The concentrations of water-soluble carbohydrates decreased by more than 50%; the ammonia-N concentrations increased 40%, and pH increased by more than 1 unit as a result of exposure to air. These changes were less in forage that was treated with the additive at chopping. After 60 d, silages of forages that were exposed to air before ensiling had a higher pH, higher concentrations of ammonia-N and butyric acid, and lower concentrations of lactic and acetic acids than silages of forage that had been ensiled immediately after harvest. In situ DM digestibility was lowest in untreated silages that had been exposed to air before ensiling. In contrast, treatment with the additive, applied before or after exposure to air, prevented the reduction in in vitro digestion.

The effect of treating whole-plant barley with Lactobacillus buchneri 40788 on silage fermentation, aerobic stability, and nutritive value for dairy cows

Chopped barley forage was ensiled untreated or treated with several doses (1 x 10(5) to 1 x 10(6) cfu/g of fresh forage) of Lactobacillus buchneri 40788 in laboratory silos and untreated or treated (4 x 10(5) cfu/g) in a farm silo. Silage from the farm silos was fed to lactating cows. In the laboratory silo, the effects of inoculation on fermentation and aerobic stability were also compared to silage treated with a commercial inoculant and a buffered propionic acid additive. Inoculation with L. buchneri 40788 decreased the final concentrations of lactic acid but increased concentrations of acetic acid and ethanol in silage from laboratory and farm silos. Silages stored in laboratory silos did not heat after exposure to air for 7 d and were then mixed with alfalfa silage and a concentrate to form total mixed rations (TMR) that were further exposed to air. The TMR containing silages treated with L. buchneri 40788 or a buffered propionic-acid-based additive took longer to heat and spoil than the TMR containing untreated silage or silagetreated with the commercial inoculant. Silage stored in a farm silo and treated with L. buchneri 40788 had fewer yeasts and molds than did untreated silage. Aerobic stability was greater in treated silage alone and in a TMR containing treated silage. Dry matter intake (18.6 kg/d), milk production (25.7 kg/d), and milk composition did not differ between cows fed a TMR containinguntreated or treated silage. These findings show that L. buchneri can improve the aerobic stability of barley silage in laboratory and farm silos and that feeding treated silage had no negative effect on intake or performance.

Accommodation of couch constraints for coplanar intensity modulated radiation therapy

PURPOSE

Three treatment couches, henceforth referred to as the standard, the variable standard and the C-arm couch, each based on a different supporting frame system, were investigated for their suitability for the delivery of a high number of coplanar beams (> or =5) as may be required for intensity-modulated radiation therapy treatments.

MATERIALS AND METHODS

A number of equispaced beam arrangements (five to nine) were examined in combination with two circular target sizes (Phi6 and Phi10 cm) at different locations within an elliptical body on the investigated couches, resulting in 70 different plans per couch. A rule based advisory system determined possible intersections of the beam paths with the supporting frames of the respective treatment couch and suggested a suitable constellation for the supporting frames. In cases of intersection, a beam-couch collision was eliminated by minimal rotation of the beams from the initial equispaced beam arrangement. To investigate the effect of a rotation of the posterior-oblique beams for five, seven and nine initially equispaced beams by an angle of 10 degrees, a prostate plan was generated and compared with equispaced beam arrangement.

RESULTS

Initial beam paths intersected with the standard couch in 63% of the plans, necessitating a rotation of one or two beams. It was necessary to modify the beam angles in 34% of the cases on the variable standard couch to avoid an intersection of the beams with the couch. All the plans would have been delivered satisfactorily on the C-arm couch without a rotation of beams. Simulation studies showed that the dose distribution for a prostate treatment could be affected significantly, but not detrimentally, by the rotation of the two posterior-oblique beam orientations by an angle of 10 degrees.

A mechanistic model of whole-tract digestion and methanogenesis in the lactating dairy cow: model development, evaluation, and application

Dietary intervention to reduce methane emissions from lactating dairy cattle is both environmentally and nutritionally desirable due to the importance of methane as a causative agent in global warming and as a significant loss of feed energy. Reliable prediction systems for methane production over a range of dietary inputs could be used to develop novel dietary regimes for the limitation of feed energy loss to methane. This investigation builds on previous attempts at modeling methanogenesis and involves the development of a dynamic mechanistic model of wholerumen function. The model incorporates modifications to certain ruminal fermentation parameters and the addition of a postruminal digestive element. Regression analysis showed good agreement between observed and predicted results for experimental data taken from the literature (r2 = 0.76, root mean square prediction error = 15.4%). Evaluation of model predictions for experimental observations from five calorimetry studies (67 observations) with lactating dairy cows at the Centre for Dairy Research, in Reading, U.K., shows an underprediction (2.1 MJ/d) of methane production (r2 = 0.46, root mean square prediction error = 12.4%). Application of the model to develop diets for minimizing methanogenesis indicated a need to limit the ratio of lipogenic to glucogenic VFA in the rumen and hindgut. This may be achieved by replacing soluble sugars in the concentrate with starch or substituting corn silage for grass silage. On a herd basis, the model predicted that increasing dietary energy intake per cow can minimize the annual loss of feed energy through methane production. The mechanistic model is a valuable tool for predicting methane emissions from dairy cows.

Some limitations in the practical delivery of intensity modulated radiation therapy

The resolution characteristics of intensity modulated beam (IMB) profiles produced by milled compensators and by multileaf collimators (MLCs) are independently investigated with respect to the primary fluence. It is shown that both methods have different characteristics in the longitudinal and lateral direction and, as a consequence, the resolutions of the longitudinal and lateral delivered IMB profiles differ. For both methods, the restrictions are identified. For compensators, the maximum slopes in the machining process, which should not be exceeded, are quantified. For MLCs, emphasis is given to the direction perpendicular to leaf movement. A number of test modulations were created and the effect of different size MLCs on the intensity profile revealed that unacceptable errors can be introduced if the profiles are heavily modulated. The production of intensity modulated radiation therapy (IMRT) beams by both machined compensators or by MLCs is limited by physical constraints. Having identified these constraints, some steps should now be taken to accommodate them either in the objective function for the calculation of the beam profiles or in the delivery system.

Mechanisms of maternal aneuploidy: FISH analysis of oocytes and polar bodies in patients undergoing assisted conception

We have examined unfertilised oocytes and their first polar bodies (PBs) to determine the way in which the frequency of whole chromosome imbalance compares with that involving single chromatids and whether the precocious separation of chromatids prior to anaphase I affects all pairs of chromosomes. We have applied the technique of fluorescent in situ hybridisation in a three-stage method by using locus-specific probes for chromosomes 13 and 21 and alpha-satellite probes for chromosomes 1, 9, 16, 18 and X to determine the chromosome status of oocytes and their PBs. We obtained analysable results from 127 oocytes and 57 PBs from 72 patients of average age 33 years. Six oocytes and three PBs had extra signals but, of these, three were derived from a single patient, aged 26. Anomalies were seen in chromosomes 13, 16, 18, X and, notably, 21 but none were observed in chromosomes 1 and 9. Half of the anomalies involved additional chromatids rather than whole chromosomes. Since particular chromatids were found to be prematurely separated in the metaphase II oocyte, this may provide further evidence for an additional mechanism of maternal aneuploidy that operates at anaphase II. Detailed analyses of both oocytes and PBs have elucidated possible mechanisms leading to aneuploid gametes in this group of patients with fertility problems.

An investigation into the use of polymer gel dosimetry in low dose rate brachytherapy

An investigation has been carried out into the properties of the BANG polymer gel and its use in the dosimetry of low dose rate brachytherapy. It was discovered that the response of the gel was reproducible and linear to 10 Gy. The gel was found to be tissue equivalent with a response independent of energy to within experimental accuracy (standard error of measurement +/- 5%). The slope of the calibration curve was found to increase from 0.28 +/- 0.01 s-1 Gy-1 to 0.50 +/- 0.02 s-1 Gy-1 for an increase in monomer concentration from 6 to 9%. Absorbed dose distributions for a straight applicator containing 36 137Cs sources were measured using the gel and the results compared with measurements made with thermoluminescent dosemeters (TLDs) and calculated values. Good agreement was found for the relative measurements. The root mean square residual percentage errors were 3%, 1% and 4% for the gel and the two groups of TLDs, respectively. There were some significant differences in absolute values of absorbed dose in the gel, possibly owing to the effects of oxygen. Measurements of a complex gynaecological insert were also made and compared with isodose curves from a planning system (Helax TMS), and in areas unaffected by oxygen diffusion the isodose levels from 100 to 50% agreed to within less than 0.5 mm.

Regulation of sulphotransferase expression in the endometrium during the menstrual cycle, by oral contraceptives and during early pregnancy

The endometrium plays a key role in reproduction, and this function is tightly regulated by endogenous and xenobiotic steroids. Sulphation, catalysed by members of the sulphotransferase (SULT) enzyme family, is a major deactivating mechanism for steroid hormones and we have investigated the expression and regulation in vivo of SULT in the human endometrium. In the normal cycling endometrium, expression of the phenol sulphotransferases SULT1A1 and SULT1A3 and the oestrogen sulphotransferase SULT1E1 were observed, with SULT1A1 and SULT1E1 expression being higher in the luteal phase than in the follicular phase. No expression of the hydroxysteroid sulphotransferase SULT2A1 was detected at any time in the endometrium. In endometrium from women taking the combined oral contraceptive pill (OCP), SULT1E1 expression was virtually absent, and SULT1A1 expression was substantially reduced. Similarly, in early pregnancy (i.e. first trimester) endometrium, SULT1E1 expression was absent, although SULT1A1 and SULT1A3 expression were unaffected. Our results with normal endometrium support in-vitro data showing that SULT1E1 expression is regulated by progesterone. However, the data obtained from OCP and early pregnancy endometrium suggest that factors other than the concentration of circulating progesterone are involved in the regulation of the expression of this important enzyme in the endometrium.

Optimization of beam orientation in radiotherapy using planar geometry

This paper proposes a new geometrical formulation of the coplanar beam orientation problem combined with a hybrid multiobjective genetic algorithm. The approach is demonstrated by optimizing the beam orientation in two dimensions, with the objectives being formulated using planar geometry. The traditional formulation of the objectives associated with the organs at risk has been modified to account for the use of complex dose delivery techniques such as beam intensity modulation. The new algorithm attempts to replicate the approach of a treatment planner whilst reducing the amount of computation required. Hybrid genetic search operators have been developed to improve the performance of the genetic algorithm by exploiting problem-specific features. The multiobjective genetic algorithm is formulated around the concept of Pareto optimality which enables the algorithm to search in parallel for different objectives. When the approach is applied without constraining the number of beams, the solution produces an indication of the minimum number of beams required. It is also possible to obtain non-dominated solutions for various numbers of beams, thereby giving the clinicians a choice in terms of the number of beams as well as in the orientation of these beams.

A philosophical approach to treatment machine maintenance and breakdown

Planned preventative maintenance (PPM), quality control (QC) checks and breakdown all contribute to the down-time of a radiotherapy treatment machine. Low levels of machine availability are unacceptable both clinically and financially. Clinical data demonstrate that, for many tumours, interruptions to treatment will result in reduced local control. Reductions to the gaps in treatment can be achieved by patient interchange between machines. Maintaining the maximum possible machine availability will reduce the potential for errors associated with the transfer of patients between machines, and reduce the cost of treatment. Practices for routine PPM and QC vary between hospitals. In this report, a rationale for breakdown and maintenance will be described. Based on the faults experienced on a Philips SL 75-5 and a Philips SL25 over a period of 3 years, the workload associated with routine maintenance and quality control are presented and the additional work associated with breakdown discussed. Faults have been categorized on a scale between catastrophe and maintainability. A demonstration of how this analysis can be used to assess the cost-benefits of proposed changes in working patterns by the extension or reduction of maintenance periods is provided. The results indicated that no gain would be made in changing from a 1-day to a 2-day per month PPM schedule.

Demonstration of a combined filter to improve the field uniformity of a 90 kV superficial X-ray therapy machine for different treatment field sizes

The field uniformity of a superficial X-ray machine operating at 90 kV, 10 mA and filtered with a 1.1 mm aluminium beam hardening filter was investigated at a depth of 1 cm below the surface. Uniformity measurements were carried out using films and a densitometer to detect the relative absorbed dose across the field. Film dosimetry was assessed by comparison with ionization chamber dosimetry in a water tank. The original flat hardening aluminium filter was replaced by a combined, profiled filter to improve the uniformity across field sizes 20 cm, 5 cm and 2 cm diameter as well as hardening the beam. Flatness of the beam profile was improved for the 20 cm field size from +/-7.5% to +/-1.3% across the anode/cathode direction and from +/-7.9% to +/-4.7% in the anode/cathode direction. For the 5 cm field size the improvement was from +/-4% to +/-3% and from +/-5.3% to +/-3.6% and for 2 cm field size from +/-3.4% to +/-2.8% and from 10.5% to +/-9.7% in the same directions, respectively. Beam quality measurements were made and the original half-value-layer was reduced from 2.21 +/- 0.09 mm to 2.07 +/- 0.09 mm. The project demonstrated that it was possible to build a filter capable of flattening the beam profile for different sized applicators without significantly changing the penetrating ability of the beam.

Design, production and characterization of antibodies discriminating between the phenol- and monoamine-sulphating forms of human phenol sulphotransferase

1. Phenol sulphotransferases (PSTs) are important enzymes in xenobiotic and endobiotic detoxication, and a key component of the body's chemical defence mechanism. 2. Human phenol-(P-PST) and monoamine-(M-PST) sulphating forms of PST share 93% amino acid sequence identity, and to date the various antibodies produced against PSTs all recognize both enzymes. 3. We have identified two peptides based on the cDNA-derived amino acid sequences of human P-PST and M-PST, which elicited for the first time antibodies capable of discriminating between these highly homologous enzymes. 4. These antibodies represent valuable tools for studying the expression, distribution and function of human phenol sulphotransferases.

Bone scanning in the multiply injured patient

A prospective study was undertaken to evaluate the role of radionuclide bone scanning in the management of patients with multiple injuries. During a 7 month period, 14 patients with multiple injuries underwent a bone scan in order to identify occult skeletal injuries. All of the patients had new injuries diagnosed. The majority of new injuries occurred either in a limb in which an injury had already been diagnosed at presentation, or in the chest. Such findings are consistent with previously published data. Infrequently, there was a change in management of the patients in this series following the bone scan.

Loci of Mycobacterium avium ser2 gene cluster and their functions

The highly antigenic glycopeptidolipids present on the surface of members of the Mycobacterium avium complex serve to distinguish these bacteria from all others and to define the various serovars that compose this complex. Previously, the genes responsible for the biosynthesis of the disaccharide hapten [2,3-di-O-methyl-alpha-L-fucopyranosyl-(1-->3)-alpha-L-rhamnopyranose] of serovar 2 of the M. avium complex were isolated, localized to a contiguous 22- to 27-kb fragment of the M. avium genome, and designated the ser2 gene cluster (J. T. Belisle, L. Pascopella, J. M. Inamine, P. J. Brennan, and W. R. Jacobs, Jr., J. Bacteriol. 173:6991-6997, 1991). In the present study, transposon saturation mutagenesis was used to map the specific genetic loci within the ser2 gene cluster required for expression of this disaccharide. Four essential loci, termed ser2A, -B, -C, and -D, constituting a total of 5.7 kb within the ser2 gene cluster, were defined. The ser2B and ser2D loci encode the methyltransferases required to methylate the fucose at the 3 and 2 positions, respectively. The rhamnosyltransferase was encoded by ser2A, whereas either ser2C or ser2D encoded the fucosyltransferase. The ser2C and ser2D loci are also apparently involved in the de novo synthesis of fucose. Isolation of the truncated versions of the hapten induced by the transposon insertions provides genetic evidence that the glycopeptidolipids of M. avium serovar 2 are synthesized by an initial transfer of the rhamnose unit to the peptide core followed by fucose and finally O methylation of the fucosyl unit.

The development of an interdepartmental audit as part of a physics quality assurance programme for external beam therapy

A cost-effective audit system has been developed that will both detect systematic error in data and procedures and evaluate the quality assurance programme provided by a physics department for radiotherapy. The audit has been developed for external beam radiotherapy and assesses one modality and one treatment machine per year. The audit is carried out on an interdepartmental basis and can be undertaken by two physicists from each department in one working day. The method of assessing the quality assurance programme and the schedule of measurements are described. The process is illustrated using the results of trial audits between the medical physics departments at Coventry and Leicester.

Use of the linear quadratic model in order to accommodate a small reduction in the number of fractions of a standard radiotherapy treatment regime

Use of the linear quadratic model is considered for reduction, by one or two fractions, of the number of fractions in a daily fractionated reference schedule while maintaining a continuous regime. The cases of maintaining late or early tumour reacting tissue are considered with the inclusion of time effects. The reduction of biologically effective dose (BED) to early-tumour type tissue is shown to be overestimated for both cases if time effects are not taken into account. A third option is outlined, which equates the magnitude of the fractional reduction of BED for early-tumour-reacting tissue to the fractional increase in BED for late-reacting tissue without accounting for time effects. Using this option, the resulting variations in BED for late- and early-tumour tissue are compared with the accepted tolerances in physical dose delivery and some examples presented. The overestimated prediction of the variation in BED for early-tumour tissue still applies in this option, suggesting that this is the way the linear quadratic model should be applied to such a schedule change.

Steroid secretion by human early embryos in culture

The ability of in-vitro fertilized human embryos to secrete oestradiol in culture in the presence of precursor androgen was demonstrated in four independent cultures. Varying amounts of oestradiol were detected and secretion was observed as early as days 5-8 post-fertilization. The pattern of human chorionic gonadotrophin secretion was similar to oestradiol secretion for individual embryos. In one additional culture, secretion of oestradiol and progesterone was observed.

Spontaneous insertion of an IS1-like element into the virF gene is responsible for avirulence in opaque colonial variants of Shigella flexneri 2a

Colonial variation of Shigella flexneri serotype 2a from the translucent (2457T) to the opaque form (2457O) occurs spontaneously once in 10(4) cell divisions, with concomitant loss of ipa gene expression and virulence. The appearance of 2457O was associated with the insertional inactivation of virF, an invasion plasmid-encoded positive regulator of ipa gene expression. Plasmid pWR110, a Tn5-tagged invasion plasmid that restores the invasive phenotype to plasmid-cured Shigella derivatives, was conjugally transferred into 2457O. Synthesis of the invasion-associated IpaB and IpaC polypeptides, normally present on the surface of virulent shigellae, and the invasive phenotype were restored in 2457O(pWR110) transconjugants. Plasmid DNA restriction endonuclease patterns of 2457T and 2457O, along with hybridization analysis, showed that a SalI fragment carrying the virF gene in 2457O had increased in size relative to its counterpart in 2457T. Analysis of virF DNA sequences amplified by the polymerase chain reaction revealed that the virF sequence from 2457O was 780 bp larger than that amplified from 2457T. Moreover, the virF sequence amplified from 2457O hybridized to an IS1 DNA probe whereas the amplified 2457T virF sequence did not. DNA sequence analysis mapped the insertion element, designated IS1SFO, within an A.T-rich region of the virF open reading frame and identified a 9-bp virF target sequence that was duplicated at the insertion site of IS1SFO. The DNA sequence of IS1SFO was greater than 99% homologous to IS1F. Plasmid pWR600, carrying a 1,260-bp HpaII fragment encoding a wild-type virF gene, was able to restore the virulent phenotype and translucent colonial morphology to nine independently isolated 2457O hosts.

Effects of in-vitro exposure to HCG on subsequent HCG-responsiveness of human granulosa cells obtained following treatment with GnRH analogue and gonadotrophins: an in-vitro model for luteal phase support

The pregnancy rate in patients undergoing assisted conception treatment following pituitary desensitization with GnRH analogue and ovarian stimulation with gonadotrophins has been reported to be higher when ovarian function is supported in the luteal phase by exogenous human chorionic gonadotrophin (HCG). In the present study, we have examined the effects of culturing monolayers of granulosa cells, collected from such patients at oocyte retrieval, for various time intervals in the presence or absence of HCG on their subsequent ability to secrete progesterone (P4) either spontaneously or in response to further challenge with HCG. When cultured in the absence of HCG, granulosa cells demonstrated a rapid decline in both the spontaneous P4 secretion rate and the ability to secrete P4 in response to HCG. Maintenance in the presence of HCG inhibited the rapid decline in ability to secrete P4 spontaneously and also significantly enhanced the ability to respond to subsequent HCG stimulation. These results suggest that HCG support in the luteal phase in GnRH analogue-treated patients may have a cellular basis for its action both in maintenance of P4 secretion and also in rendering the corpus luteum more sensitive to rescue by conceptus-derived HCG.

Clinical and biochemical pregnancy in two respective recipients without ovarian function following gamete intrafallopian transfers using oocytes from a single donor

Infertility resulting from premature ovarian failure in two independent patients was treated using a combination of steroid replacement, oocyte donation and gamete intrafallopian transfer (GIFT). Following ovarian stimulation four oocytes were retrieved from a volunteer donor undergoing simultaneous laparoscopic sterilisation. Two oocytes were subsequently replaced into each recipient's fallopian tube together with capacitated sperm from their respective husbands. In one recipient (Turner's syndrome) an intrauterine sac with fetal heart present was observed by ultrasound six weeks post GIFT whereas in the second recipient (premature menopause) plasma beta-hCG reached a peak value of 954mIU/ml eighteen days after GIFT before decreasing rapidly in the absence of ultrasound evidence of pregnancy. Intramuscular administration of progesterone appeared to be necessary during the post-GIFT period for maintenance of pregnancy. The above treatment was carried out on a predominantly out-patient basis in a small assisted conception unit based in a teaching hospital.

The American College of Rheumatology 1990 criteria for the classification of Henoch-Schönlein purpura

Criteria for identifying Henoch-Schönlein Purpura (HSP) and distinguishing HSP from other forms of systemic arteritis were developed by comparing the manifestations in 85 patients who had HSP with those of 722 control patients with other forms of vasculitis. By the traditional format of choosing different combinations of candidate criteria and comparing the combinations for their ability to separate HSP cases from controls, 4 criteria were identified: age less than or equal to 20 years at disease onset, palpable purpura, acute abdominal pain, and biopsy showing granulocytes in the walls of small arterioles or venules. The presence of any 2 or more of these criteria distinguish HSP from other forms of vasculitis with a sensitivity of 87.1% and a specificity of 87.7%. The criteria selected by a classification tree method were similar: palpable purpura, age less than or equal to 20 years at disease onset, biopsy showing granulocytes around arterioles or venules, and gastrointestinal bleeding. These were able to distinguish HSP from other forms of vasculitis with a sensitivity of 89.4% and a specificity of 88.1%.

Molecular characterization of a trans-acting, positive effector (ipaR) of invasion plasmid antigen synthesis in Shigella flexneri serotype 5

A trans-acting, positive effector of invasion plasmid antigen (Ipa) synthesis has been identified and mapped on the pWR100 invasion plasmid of Shigella flexneri serotype 5 (strain M90T-W). Recombinant plasmids carrying this regulatory gene, designated ipaR, were found to restore full virulence to a non-invasive ipaR::Tn5 insertion mutant [M90T-W(pHS1042)] that had lost the ability to synthesize four Ipa antigens (IpaA, 70 kDa; IpaB, 62 kDa; IpaC, 42 kDa; and IpaD, 37 kDa). Genetic mapping of the ipaR gene positioned the locus on a 2.6 kb PstI-AccI fragment contained within a larger 8.0 kb EcoRI molecule that also encoded IpaD, IpaA, and two small proteins (27 kDa and 28 kDa). The trans regulatory effect of the ipaR product on ipaB, ipaC, ipaD, and ipaA expression was demonstrated by transforming compatible ipaBC, ipaDA, ipaR and ipaDAR plasmid recombinants, in various combinations, into M90T-A3, an isogenic invasion plasmid mutant of M90T-W that contained a deletion of the pWR100 ipaBCDA and ipaR loci; such transformants produced wild type levels of the IpaB, IpaC, IpaD and IpaA antigens only in the presence of IpaR+ plasmids. DNA sequence analysis of the ipaR region established that the intiation codon for ipaR is 459 bp from the 3'-end of the ipaA gene and that ipaR encodes a 309 amino acid residue protein. An interesting feature of the IpaR polypeptide was its strong sequence homology with the bacteriophage P1 partition protein ParB, consisting of a 42.8% amino acid identity over a 278 residue section of the aligned proteins.

Mercury levels in the plumage of red-billed gulls Larus novaehollandiae scopulinus of known sex and age

Samples of 4-8 small body feathers were taken from 27 chicks and 35 adult red-billed gulls caught at their nests on the Kaikoura Peninsula, New Zealand, in December 1988. The adults had been ringed as chicks and were of known ages from 2 to 15 years old. Analysis of total mercury in the feather samples showed that levels were independent of sex and age in adults. Mean fresh weight concentration in adult body feathers was 2.4 microg g(-1). The lack of age accumulation of mercury in gull feathers contrasts with the well known age related accumulation of mercury in tissues of fish and marine mammals, but agrees with predictions of recent studies on mercury dynamics in birds. Mercury levels in chick feathers were about 80% of levels in adult feathers.