The effect of perioperative allergic conjunctivitis on corneal lymphangiogenesis after corneal transplantation

INTRODUCTION

Perioperative allergic conjunctivitis accelerates the speed of corneal allograft rejection. This study examines the effect of allergic conjunctivitis, with and without dexamethasone treatment, on the early inflammatory response and lymphangiogenesis in the host cornea following corneal transplantation.

METHODS

Allogeneic fully MHC-mismatched C57Bl/6 strain donor corneas were transplanted into naive A/J mice and into A/J mice with active allergic conjunctivitis. Further groups of allograft recipients with allergic conjunctivitis were treated post-operatively with twice daily topical dexamethasone 0.1% or phosphate-buffered saline. Mice were killed on days 2 and 6 and corneas were examined by (i) fluorescent immunohistochemistry of frozen sections using anti-CD11b, anti-F4/80 and anti-Gr-1 antibodies, or (ii) whole-mount staining with anti-LYVE-1 antibody. Lymphatic ingrowth and numbers of cells infiltrating the host cornea were compared between groups.

RESULTS

There were significantly higher numbers of CD11b(+) cells and LYVE-1(+) vessels in the host cornea at day 2 in allergic compared with naive recipients, but no differences between naive and allergic recipients at day 6. In allergic eyes, dexamethasone treatment significantly inhibited LYVE-1 expression at days 2 and 6, and significantly improved allograft survival in recipients with allergic conjunctivitis if maintained for a week.

CONCLUSIONS

The innate immune response to allogeneic corneal tissue is more vigorous in the presence of allergic conjunctivitis than in naive eyes and is associated with accelerated lymphatic ingrowth to host cornea. Topical dexamethasone inhibits lymphatic ingrowth and this may be one mechanism by which topical steroid enhances graft survival.

The effects of acute dynamic exercise on haemostasis in fi rst class Scottish football referees

PURPOSE

Physical fitness may confer protection from thrombosis; however, exercise-induced platelet activation may be involved in the triggering of acute vascular events. This study aimed to assess haemostatic responses to acute exercise in trained and sedentary middle-aged subjects.

METHODS

21 first class Scottish football referees and 15 sedentary controls performed a treadmill exercise test. Blood sampling was performed before, immediately after and 30 minutes post-exercise. Samples were analysed for platelet count, prothrombin time, activated partial thromboplastin time (APTT) and serum fibrinogen. Platelet activation was assessed using flow cytometry with CD62 (P-selectin) and antifibrinogen antibodies at rest and in response to ADP and epinephrine.

RESULTS

Mean maximal oxygen consumption (Vo2) (ml/kg per minute) achieved was 47.23 (5.02) in the referees and 30.1 (5.2) in sedentary controls. Total platelet count (x10(-9)/l) increased immediately post-exercise (228.2 (40.5), 278.6 (48.9) p=0.001) remaining elevated at 30 minutes in both groups. APTT (s) was reduced immediately post-exercise (32.15 (3.1), 29.7 (3.94) p=0.001) with a further reduction seen at 30 minutes (32.15 (3.1), 28.4 (3.31) p=0.001). In the referees, percentage CD62 expression increased immediately post-exercise (0.688 (0.52), 1.42 (1.3) p=0.008). Percentage antifibrinogen expression increased post-exercise (5.19 (4.31), 13.01 (14.24) p=0.017), with a further increase at 30 minutes (5.19 (4.31), 20.47 (26.8) p=0.02). Similar trends were seen in sedentary controls.

CONCLUSION

This study suggests that in an older athletic population, physical fitness does not protect against the prothrombotic effects of exercise. These data suggest that during a football match when referees achieve approximately 80% of peak VO2 (23) they may be at risk of significant platelet activation. Prophylactic platelet inhibition should be considered in this group after appropriate screening and risk stratification.

Phase I pharmacokinetic and pharmacodynamic study of the bioreductive drug RH1

BACKGROUND

This trial describes a first-in-man evaluation of RH1, a novel bioreductive drug activated by DT-diaphorase (DTD), an enzyme overexpressed in many tumours.

PATIENTS AND METHODS

A dose-escalation phase I trial of RH1 was carried out. The primary objective was to establish the maximum tolerated dose (MTD) of RH1. Secondary objectives were assessment of toxicity, pharmacokinetic determination of RH1 and pharmacodynamic assessment of drug effect through measurement of DNA cross linking in peripheral blood mononuclear cells (PBMCs) and tumour, DTD activity in tumour and NAD(P)H:quinone oxidoreductase 1 (NQO1) polymorphism status.

RESULTS

Eighteen patients of World Health Organization performance status of zero to one with advanced refractory solid malignancies were enrolled. MTD was 1430 μg/m(2)/day with reversible bone marrow suppression being dose limiting. Plasma pharmacokinetic analysis showed RH1 is rapidly cleared from blood (t(1/2) = 12.3 min), with AUC increasing proportionately with dose. The comet-X assay demonstrated dose-related increases in DNA cross linking in PBMCs. DNA cross linking was demonstrated in tumours, even with low levels of DTD. Only one patient was homozygous for NQO1 polymorphism precluding any conclusion of its effect.

CONCLUSIONS

RH1 was well tolerated with predictable and manageable toxicity. The MTD of 1430 μg/m(2)/day is the dose recommended for phase II trials. The biomarkers of DNA cross linking, DTD activity and NQO1 status have been validated and clinically developed.

Use of ultrasonic pachymetry for measurement of changes in corneal thickness in mouse corneal transplant rejection

BACKGROUND/AIMS

Diagnosis of rejection in the mouse model of corneal transplantation is based on subjective judgement of loss of graft transparency. The aims of this study were to (1) evaluate a pachymetry technique to measure changes in mouse corneal thickness and (2) correlate increases in transplant thickness with clinical and histological features of rejection.

METHODS

Orthotopic corneal allografts (C57BL/6 strain donor) and syngeneic grafts were performed in A/J mice. Graft transparency was graded and corneal thickness measured by pachymetry on alternate days. Transverse sections of donor cornea excised from eyes representative of clinical opacity grades 1-4 were prepared, photographed, graft section thickness measured and stromal graft-infiltrating cells counted. Intraobserver and interobserver variations in pachymetry were statistically tested.

RESULTS

Graft thickness, as measured by pachymetry, increased with each clinical opacity grade. Thickness for opacity grades 0, 1 and 2 was less than 300 microm in all recipients. Graft thickness for grades 3 and 4 was greater than 300 microm in all cases. For measurements up to 400 mum, there was a good correlation between thickness as measured by in vivo pachymetry and in histopathological sections. The mean interobserver bias was -11.35 microm, while the mean intraobserver bias was +3.96 microm. Stromal cellularity increased with increasing corneal thickness up to approximately 300 microm.

CONCLUSION

In vivo graft pachymetry provides a new and reliable way to objectively diagnose rejection in the mouse model of corneal transplantation.

Final results of a phase I clinical trial of the bioreductive drug RH1

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Background: RH1 (2,5-diaziridinyl-3-[hydroxymethyl]-6-methyl-1,4-benoquinone) is a novel bioreductive drug which is activated by the two electron reductase, DT-diaphorase (DTD) (NAD(P)H:quinone oxidoreductase). DTD is over-expressed in many tumors relative to normal tissue, especially lung, breast and colorectal tumors, so it is hoped that RH1 is selectively activated in such tumours with minimal normal tissue toxicity. Methods: Under the auspices of the CR-UK Drug Development Office, a dose escalation phase I trial of RH1 was performed at two centres. The primary objective was to establish the maximum tolerated dose (MTD) of RH1 given as a 10–30 minute infusion for 5 days every 3 weeks. Toxicity was assessed according to NCI CTC V2.0 criteria. Secondary objectives were to determine RH1 pharmacokinetics (PK), DNA cross-linking in peripheral blood lymphocytes and tumour cells, DTD activity in tumour, NQO1 polymorphism status and document any anti-tumour activity. Results: Eighteen patients of WHO performance status 0–1 with advanced refractory solid malignancies were enrolled. 14 patients were male and eight patients had colorectal adenocarcinoma. The MTD was 1,430 mcg/m2/day and the dose-limiting toxicity (DLT) was bone marrow suppression. DLT occurred in both patients treated at 1,905 mcg/m2/day: one developed grade 3 thrombocytopenia with haemorrhage and grade 3 anaemia; the other died from neutropenic sepsis. Other clinically significant drug-related toxicities included moderate phlebitis and fatigue. Plasma PK analysis on days 1 and 5 in cycle 1 showed rapid plasma clearance of RH1 (t1/2=12.3 mins) with AUC increasing proportionately with dose. The comet-X assay showed increases in DNA inter-stand cross-linking in peripheral blood lymphocytes treated at 200 mcg/m2/day or above. These cross-links were detectable within one hour of commencement of dosing and reached a maximum of 30%. DNA cross-linking after RH1 was seen in tumour samples, even with low levels of DTD. One patient was homozygous for the NQO1 polymorphism. No objective tumour responses were recorded. Conclusions: The MTD of 1,430 mcg/m2/day is the dose recommended for phase II clinical trials. Tested doses were associated with DNA cross-linking in both peripheral blood lymphocytes and tumour cells.

No significant financial relationships to disclose.

Results of a phase III randomized controlled trial of the safety and efficacy of atrasentan in men with nonmetastatic hormone-refractory prostate cancer (HRPC)

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Introduction: Atrasentan is a potent oral, selective endothelin A receptor antagonist with biological activity in patients with HRPC. This randomized phase III trial of atrasentan vs placebo was conducted in 941 men with nonmetastatic HRPC whose prostate-specific antigen (PSA) was rising despite adequate androgen suppression. Methods: 467 patients were randomized to receive atrasentan 10 mg and 474 patients were randomized to receive placebo daily. Primary efficacy endpoints were time to disease progression (TTP) and progression-free survival, with progression defined as the onset of metastases. Secondary endpoints were overall survival, time to PSA progression, change from baseline in bone alkaline phosphatase (BAP), and PSA doubling time (PSADT). Results: In the intent-to-treat population, median TTP was 764 days with atrasentan and 671 days with placebo (hazard ratio [HR], 0.915; G1,1 P=0.288). More placebo- treated patients (267, 56.3%) than atrasentan-treated patients (227, 48.6%) experienced disease progression. Overall, 278 patients (29.5%) discontinued before reaching a protocol-defined endpoint (155, 40.8% US vs 123, 21.6% non-US). More placebo-treated patients (210, 44.3%) than atrasentan-treated patients (169, 36.2%) experienced new skeletal lesions. Median survival was 1,477 days for the atrasentan group and 1,403 days for the placebo group (HR, 0.909; G1,1 P=0.176). Mean change from baseline to final BAP was -1.51 IU/L with atrasentan compared with +2.20 IU/L with placebo (P<0.001). PSADT was lengthened with atrasentan relative to placebo (P<0.031). The incidence of peripheral edema, nasal congestion, headache, dyspnea, anemia, and heart failure was significantly greater in the atrasentan group (P<0.05). Most of these events were mild and nonserious and did not result in study discontinuation. Conclusions: Data from this study did not show a statistically significant difference in time to progression between atrasentan and placebo. However, the high discontinuation rate, especially among US patients, may have compromised the ability of the study to accurately determine the treatment effect of atrasentan in this population.

No significant financial relationships to disclose.

Bovine spongiform encephalopathy: the effect of oral exposure dose on attack rate and incubation period in cattle

The dose–response of cattle exposed to the bovine spongiform encephalopathy (BSE) agent is an important component of modelling exposure risks for animals and humans and thereby, the modulation of surveillance and control strategies for BSE. In two experiments calves were dosed orally with a range of amounts of a pool of brainstems from BSE-affected cattle. Infectivity in the pool was determined by end-point titration in mice. Recipient cattle were monitored for clinical disease and, from the incidence of pathologically confirmed cases and their incubation periods (IPs), the attack rate and IP distribution according to dose were estimated. The dose at which 50 % of cattle would be clinically affected was estimated at 0.20 g brain material used in the experiment, with 95 % confidence intervals of 0.04–1.00 g. The IP was highly variable across all dose groups and followed a log-normal distribution, with decreasing mean as dose increased. There was no evidence of a threshold dose at which the probability of infection became vanishingly small, with 1/15 (7 %) of animals affected at the lowest dose (1 mg).

PrP genotype progression in flocks participating in the National Scrapie Plan for Great Britain

The National Scrapie Plan (NSP) for Great Britain is a voluntary scheme that, through PrP genotype testing and restricted breeding, aims to reduce the risk of scrapie in the national sheep flock. To gauge the progress in member flocks and within breeds, the genotype profile of successive crops of ram lambs was monitored between 2002 and 2004. In each of the 11 most frequently sampled breeds, the proportion of ram lambs testing in the most resistant genotype category (NSP type 1: ARR/ARR) increased, and there was a reduction in the proportion of genotypes associated with the highest disease risk, that is X/VRQ, where X is an allele other than ARR. Changes in the proportion of ram lambs testing for ARR-heterozygous genotypes (NSP type 2: ARR/X, where X is not VRQ) appeared to be influenced by whether the sheep were hill breeds or non-hill breeds. In each of six frequently sampled hill breeds these genotypes expanded, in relative terms, whereas they declined in four of five prominent lowland/crossing breeds. The proportion of ram lambs that carried neither ARR nor VRQ (NSP type 3) declined consistently in the top 11 breeds, but there was little change in the ARR/VRQ genotype (NSP type 4). Among individual flocks that had ram lambs tested in all three years 2002 to 2004, the majority experienced an increase in the proportion testing ARR/ARR, and of those that had VRQ ram lambs in 2002, most recorded a decrease in their frequency by 2004.

Cognitive mechanisms, specificity and neural underpinnings of visuospatial peaks in autism

In order to explain the cognitive and cerebral mechanisms responsible for the visuospatial peak in autism, and to document its specificity to this condition, a group of eight high-functioning individuals with autism and a visuospatial peak (HFA-P) performed a modified block-design task (BDT; subtest from Wechsler scales) at various levels of perceptual cohesiveness, as well as tasks tapping visuomotor speed, global perception, visual memory, visual search and speed of visual encoding. Their performance was compared with that of 8 autistics without a visuospatial peak (HFA-NP), 10 typically developing individuals (TD) and 8 gifted comparison participants with a visuospatial peak (TD-P). Both HFA-P and HFA-NP groups presented with diminished detrimental influence of increasing perceptual coherence compared with their BDT-matched comparison groups. Neither autistic group displayed a deficit in construction of global representations. The HFA-P group showed no differences in performance level or profile in comparison with the gifted BDT-matched [i.e. higher full-scale IQ (FSIQ)] group, apart from locally oriented perception. Diminished detrimental influence of perceptual coherence on BDT performance is both sensitive and specific to autism, and superior low-level processing interacts with locally oriented bias to produce outstanding BDT performance in a subgroup of autistic individuals. Locally oriented processing, enhanced performance in multiple tasks relying on detection of simple visual material and enhanced discrimination of first-order gratings converge towards an enhanced functioning and role of the primary visual cortex (V1) in autism. In contrast, superior or typical performance of autistics in tasks requiring global processing is inconsistent with the global-deficit-driven Weak Central Coherence hypothesis and its neurobiological magnocellular deficit counterpart.

Frequencies of PrP genotypes in 38 breeds of sheep sampled in the National Scrapie Plan for Great Britain

Between October 2001 and January 2003 the prion protein (PrP) genotypes of over 250,000 sheep were determined through the operation of the National Scrapie Plan (NSP); the results for 38 breeds were analysed to provide an estimate of the underlying PrP genotype distribution of the British sheep population. Although there was marked variability among the genotype profiles of the different breeds, several trends emerged. A comparison of the allele frequencies demonstrated that the breeds could be grouped into three categories: breeds dominated by ARR and ARQ in which the frequency of ARR exceeded the frequency of ARQ; breeds dominated by ARR and ARQ in which the frequency of ARQ exceeded the frequency of ARR; and breeds with significant levels of either AHQ, ARH or VRQ. Hill breeds were more likely to have a lower proportion of animals at low risk of scrapie (NSP type 1) and a higher proportion of animals at an intermediate risk of scrapie (NSP type 3) than other breeds. Most breeds had a small proportion of animals at high risk of scrapie (NSP type 5). The frequency of ARR/VRQ (NSP type 4) was variable.

PrP genotypes of rare breeds of sheep in Great Britain

In total 31,669 blood samples were collected from 1187 flocks of 27 rare breeds of sheep in the UK, and their genotype profiles at the prion protein locus were determined. The frequencies of the five alleles varied widely among the breeds and some had only two of the alleles and others had all five; the average was three. The average allele frequencies across all 27 breeds were 49.7 per cent for ARR, 4.4 per cent for AHQ, 2.7 per cent for ARH, 37.4 per cent for ARQ and 5.8 per cent for VRQ. The highest frequencies for each allele were 90.7 per cent for ARR in the Leicester Longwool, 24.7 per cent for AHQ in the Hebridean, 68.7 per cent for ARH in the Manx Loghtan, 98.7 per cent for ARQ in the North Ronaldsay and 28.4 per cent for VRQ in the Boreray. All 27 breeds had the ARR allele, 21 had AHQ, 11 had ARH, 26 had ARQ and 20 had VRQ.