Methods to Enhance the Metabolic Stability of Peptide-Based PET Radiopharmaceuticals

The high affinity and specificity of peptides towards biological targets, in addition to their favorable pharmacological properties, has encouraged the development of many peptide-based pharmaceuticals, including peptide-based positron emission tomography (PET) radiopharmaceuticals. However, the poor in vivo stability of unmodified peptides against proteolysis is a major challenge that must be overcome, as it can result in an impractically short in vivo biological half-life and a subsequently poor bioavailability when used in imaging and therapeutic applications. Consequently, many biologically and pharmacologically interesting peptide-based drugs may never see application. A potential way to overcome this is using peptide analogues designed to mimic the pharmacophore of a native peptide while also containing unnatural modifications that act to maintain or improve the pharmacological properties. This review explores strategies that have been developed to increase the metabolic stability of peptide-based pharmaceuticals. It includes modifications of the C- and/or N-termini, introduction of d- or other unnatural amino acids, backbone modification, PEGylation and alkyl chain incorporation, cyclization and peptide bond substitution, and where those strategies have been, or could be, applied to PET peptide-based radiopharmaceuticals.

Cardiac Leiomyosarcoma in a Cat Presenting for Bilateral Renal Neoplasia

A 10-year-old neutered female domestic longhair cat was presented to a tertiary care veterinary hospital for evaluation of a right renal mass that was identified incidentally on abdominal radiographs and classified further as a sarcoma based on fine needle aspiration cytology. Further diagnostic workup, including ultrasound and cytology, identified a sarcoma in the left kidney. After approximately 1 month of conservative medical management, the clinical condition deteriorated and the cat was humanely destroyed. Post-mortem examination confirmed bilateral renal masses with multifocal infarction and extensive necrosis, and further identified a large mass at the apex of the heart as well as multiple pulmonary nodules. Microscopical examination of the masses identified a population of poorly-differentiated neoplastic spindle cells, consistent with sarcoma. Immunohistochemically, the neoplastic cells expressed smooth muscle actin and muscle-specific actin, but were negative for myoglobin and factor VIII. Phosphotungstic acid-haematoxylin staining was unable to identify cross-striations in the neoplastic cells. Based on these results and the pattern of lesion distribution, the cat was diagnosed with cardiac leiomyosarcoma with pulmonary and bilateral renal metastasis.

Treatment outcomes and prognostic factors of feline splenic mast cell tumors: A multi-institutional retrospective study of 64 cases

BACKGROUND

Mast cell tumors (MCT) are common splenic tumors in cats, but there is limited information on treatment outcomes of cats with this disease.

MATERIALS AND METHODS

This retrospective study evaluated treatment outcomes in 64 cats with splenic MCT. Cats were categorized into the following treatment groups: splenectomy (A, n = 20); splenectomy with chemotherapy (B, n = 20); chemotherapy alone (C, n = 15); or supportive care (D, n = 9).

RESULTS

Median tumor specific survival (MTSS) was: 856, 853, 244, 365 days for groups A, B, C, and D, respectively. The MTSS was not significantly different between the 4 groups. However, comparing cats that had splenectomy (A and B) versus those that did not (C and D), the MTSS was 856 and 342 days, respectively (p=0.008). None of the prognostic factors analyzed significantly influenced survival.

CONCLUSION

Splenectomy (+/- chemotherapy) significantly prolongs survival in cats with mast cell tumors. The role of chemotherapy remains unknown.

Description of a new octoploid frog species (Anura: Pipidae: Xenopus) from the Democratic Republic of the Congo, with a discussion of the biogeography of African clawed frogs in the Albertine Rift

We describe a new octoploid species of African clawed frog (Xenopus) from the Lendu Plateau in the northern Albertine Rift of eastern Democratic Republic of the Congo. This species is the sister taxon of Xenopus vestitus (another octoploid), but is distinguished by a unique morphology, vocalization and molecular divergence in mitochondrial and autosomal DNA. Using a comprehensive genetic sample, we provide new information on the species ranges and intra-specific diversity of African clawed frogs from the Albertine Rift, including the details of a small range extension for the critically endangered Xenopus itombwensis and previously uncharacterized variation in Xenopus laevis. We also detail a new method for generating cytogenetic preparations in the field that can be stored at room temperature for up to 3 weeks. While extending our understanding of the extant diversity in the Albertine Rift, this new species highlights components of species diversity in ancestral African clawed frogs that are not represented by known extant descendants.

The inflammatory effect of cardiopulmonary bypass on leukocyte extravasation in vivo

OBJECTIVE

Extravascular trafficking of leukocytes into organs is thought to play a major role in the pathophysiologic mechanisms of the inflammatory response to cardiopulmonary bypass, yet leukocyte extravasation is difficult to study clinically. Here we have tested the hypothesis that leukocyte emigration into skin blisters can provide a way to monitor the inflammatory effect of cardiopulmonary bypass that allows testing of anti-inflammatory interventions (exemplified by aprotinin).

METHODS

Patients undergoing primary elective coronary artery bypass grafting (n = 14) were randomized into 2 equal groups to receive saline infusion during cardiopulmonary bypass (control group) or high-dose aprotinin. Experimental skin blisters (in duplicate) were induced on the forearm by means of topical application of the vesicant cantharidin, and blister fluid was sampled at 5 hours postoperatively. Inflammatory leukocyte subsets in blister fluid were analyzed by means of flow cytometry by using expression of CD11b and CD62L as a phenotypic marker of activation.

RESULTS

In the control group of patients, cardiopulmonary bypass surgery triggered a 381% increase in leukocyte extravasation into the skin compared with reference blisters carried out before surgical intervention, with neutrophil (P = .014), monocyte (P = .014), and eosinophil (P = .009) levels all statistically significantly increased. In the aprotinin group there was no statistically significant increase during cardiopulmonary bypass surgery in any inflammatory leukocyte subset. The activation phenotype of extravascular leukocytes was not significantly altered between surgical groups.

CONCLUSIONS

This study introduces the cantharidin blister technique as a powerful new research tool for analyzing the inflammatory effect of cardiopulmonary bypass in vivo. It has provided detailed molecular insight into the extravascular leukocyte population during cardiopulmonary bypass. Although aprotinin blocked cardiopulmonary bypass-dependent extravasation of leukocytes, there was no change in their CD11b/CD62L activation status. The cantharidin skin test thus represents a novel research tool for evaluating future anti-inflammatory interventions in cardiothoracic surgery.

Finding a liability-free space in which personalized medicine can bloom

Personalized medicine uses genetic and other screening tests to predict a patient's response to specific drug and biologic therapies (together "drugs"), with the aim of choosing a treatment that will provide benefits while avoiding drug-related harms. There are two schools of thought on how tort liability may affect personalized medicine, i.e., whether fear of lawsuits will tend to accelerate progress or slow it down. Tort suits include product liability suits against manufacturers and negligence suits against physicians and other providers of health-related services.

Distinguishing Product and Practice Regulation in Personalized Medicine

Protecting the public from faulty targeting of medicines, while preserving the crucial distinction between product and practice regulation, may require innovative regulatory approaches and close, ongoing involvement by the medical profession. This article explores four problem areas: validation of clinical claims for tests used in targeting therapies; developing and implementing appropriate restrictions on off-label use; promoting consistent concepts of clinical utility for use in various regulatory, reimbursement, and judicial contexts; and communication of clear information to guide clinicians in appropriate use of targeted therapeutic products. The article suggests an approach for addressing these problems by sharing regulatory activities between the Food and Drug Administration and a newly-created clinical standards board formed within the medical and scientific communities.

Hemoglobin Scavenger Receptor CD163 Mediates Interleukin-10 Release and Heme Oxygenase-1 Synthesis

The recently described hemoglobin scavenger receptor CD163 mediates the endocytosis of hemoglobin:haptoglobin (Hb:Hp) complexes and thereby counters Hb-induced oxidative tissue damage after hemolysis. Although CD163 has been indirectly associated with antiinflammatory and atheroprotective activity, no ligand-receptor-effector pathway has yet been described for this receptor. To understand the significance of CD163 and more clearly define downstream pathways linked to inflammatory resolution, we studied the expression and function of CD163 in human monocytes/macrophages using both in vitro and in vivo models. Differentiation of human blood monocytes into macrophages either by in vitro culture or in resolving cantharidin-induced skin blisters led to an equivalent increase (>15x) in CD163 expression. Elevated CD163 levels were also noted on circulating monocytes in cardiac surgical patients during the resolution phase of the systemic inflammatory response to cardiopulmonary bypass surgery. In each case, binding of Hb:Hp to CD163-bearing cells elicited potent interleukin-10 secretion, and this was inhibited by the anti-CD163 antibody RM3/1. Release of interleukin-10, in turn, induced heme oxygenase-1 stress protein synthesis via an autocrine mechanism. Such induction of heme oxygenase-1 was observed in vivo 24 to 48 hours after the onset of cardiopulmonary bypass surgery. These results identify novel antiinflammatory and cytoprotective effector pathways in human monocytes/macrophages related to Hb scavenging and metabolism, which may have relevance in atheroprotection, wound healing, and patient recovery postoperatively.

Hybridization and population genetics of two macaque species in Sulawesi, Indonesia

This study investigates hybridization and population genetics of two species of macaque monkey in Sulawesi, Indonesia, using molecular markers from mitochondrial, autosomal, and Y-chromosome DNA. Hybridization is the interbreeding of individuals from different parental taxa that are distinguishable by one or more heritable characteristics. Because hybridization can affect population structure of the parental taxa, it is an important consideration for conservation management. On the Indonesian island of Sulawesi an explosive diversification of macaques has occurred; seven of 19 species in the genus Macaca live on this island. The contact zone of the subjects of this study, M. maura and M. tonkeana, is located at the base of the southwestern peninsula of Sulawesi. Land conversion in Sulawesi is occurring at an alarming pace; currently two species of Sulawesi macaque, one of which is M. maura, are classified as endangered species. Results of this study indicate that hybridization among M. maura and M. tonkeana has led to different distributions of molecular variation in mitochondrial DNA and nuclear DNA in the contact zone; mitochondrial DNA shows a sharp transition from M. maura to M. tonkeana haplotypes, but nuclear DNA from the parental taxa is homogenized in a narrow hybrid zone. Similarly, within M. maura divergent mitochondrial DNA haplotypes are geographically structured but population subdivision in the nuclear genome is low or absent. In M. tonkeana, mitochondrial DNA haplotypes are geographically structured and a high level of nuclear DNA population subdivision is present in this species. These results are largely consistent with a macaque behavioral paradigm of female philopatry and obligate male dispersal, suggest that introgression between M. maura and M. tonkeana is restricted to the hybrid zone, and delineate one conservation management unit in M. maura and at least two in M. tonkeana.

A review of the management of 323 consecutive patients seen in a specific learning difficulties clinic

Visual correlates of specific learning difficulties (SpLD) include: binocular instability, low amplitude of accommodation, and Meares-Irlen Syndrome. Meares-Irlen Syndrome describes asthenopia and perceptual distortions which are alleviated by using individually prescribed coloured filters. Data from 323 consecutive patients seen over a 15 month period in an optometric clinic specialising in SpLD are reviewed. Visual symptoms and headaches were common. 48% of patients were given a conventional optometric intervention (spectacles, orthoptic exercises) and 50% were issued with coloured filters, usually for a trial period. 40% of those who were given orthoptic exercises were later issued with coloured overlays. 32% of those who were issued with coloured overlays were ultimately prescribed Precision Tinted lenses. Approximately half the sample were telephoned more than a year after the last clinical appointment. More than 70% of those who were prescribed Precision Tints were still wearing them daily, and results for this intervention compared favourably with data for non-tinted spectacles. The data suggest that many people with SpLD need optometric care and that the optometrist needs to be skilled in orthoptic techniques and cognisant of recent research on coloured filters.

Randomised double-masked placebo-controlled trial of a treatment for congenital nystagmus

Several therapies have been developed for congenital nystagmus (CN) but without placebo-controlled trials. We investigated a treatment which combined two therapies that had been advocated by several authors and were reported to improve visual acuity (VA). A placebo treatment was designed to mimic the time, attention, 'high tech' apparatus, and the explanation used in the experimental treatment. To each group, 38 subjects with CN were randomly allocated. Their VA and contrast sensitivity (CS) were assessed three times before undergoing treatment for 6 weeks and then once more. An improvement in VA occurred, however, this was not significantly different in the two groups. The improvement in CS was greater in the experimental than in the control group, but the difference failed to reach significance in most statistical tests. We conclude that putative therapies for CN should be assumed to be placebos until proven otherwise with randomized controlled trials.

The current practice patterns of mechanical ventilation for respiratory failure in pediatric patients

OBJECTIVE

To quantify the current practice patterns of mechanical ventilation for respiratory failure in pediatric patients.

DESIGN

Mail survey using 2 hypothetical case studies sent to pediatric critical care physicians.

MEASUREMENTS AND MAIN RESULTS

The required arterial blood gas (ABG) on conventional mechanical ventilation (CMV) is pH = 7.25 to 7.29, PO2 = 50 to 59 torr, O2 saturation = 0.85 to 0.89. Most of our survey participants will treat a patient failing conventional mechanical ventilation in their pediatric intensive care units (PICUs) with inverse ratio ventilation (IRV) (95%) and with high-frequency oscillatory ventilation (HFOV) (92%).

CONCLUSION

Most of the surveyed pediatric critical care physicians practice permissive hypercapnia in the treatment of their patients who receive ventilatory assistance. More than 90% of surveyed pediatric critical care physicians are presently using inverse ratio ventilation and high-frequency oscillatory ventilation. These data suggest that these innovative modes of therapy are already accepted as part of the standard therapeutic spectrum by the surveyed group of physicians.

The underachieving child

Visual factors in specific learning difficulties (SpLD) are reviewed. People with SpLD fail to achieve at a level that is commensurate with their intelligence. The commonest SpLD is dyslexia, which usually results from phonological processing/decoding deficits. Additionally, there are several optometric correlates of SpLD which may, in some cases, contribute to the learning difficulty. These correlates include binocular instability and a low amplitude of accommodation. Some people with reading difficulties and perceptual distortions/eyestrain can be helped by individually prescribed coloured filters. A visual processing anomaly is also often present in the form of a deficit of the transient visual system. The role of the optometrist is discussed.

Comparative molecular phylogeography of two Xenopus species, X. gilli and X. laevis, in the south-western Cape Province, South Africa

Xenopus gilli is a vulnerable anuran with a patchy distribution along the south-western coast of the Cape Province, South Africa. This species is sympatric with Xenopus laevis laevis, a widespread relative found over much of southern Africa. We examined the molecular phylogeography and population structure of the contact zone between these species to obtain information about historical biogeography and conservation management of this region. Analyses of the distribution, frequency, and cladistic and phenetic relationships among mitochondrial DNA haplotypes indicate that population subdivision is present in both taxa but that long-term isolation of sets of populations has occurred in X. gilli only. Haplotype and nucleotide diversity are also considerably higher within and among X. gilli ponds than X. l. laevis ponds in this region. We attribute the genetic segregation of X. gilli populations to ancient habitat fragmentation by ocean transgression into X. gilli habitat and to continued habitat alteration by human activity. The lower level of genetic diversity in X. L. laevis in this region is likely a result of a recent arrival of this taxon to the south-western Cape region relative to X. gilli. Population structure in X. l. laevis may be a result of isolation by distance. Clear evidence exists for at least two management units within X. gilli and strongly supports the establishment of protective measures east of False Bay in order to conserve a substantial portion of this species' extant genetic diversity.

Standardization of pyridinium crosslinks, pyridinoline and deoxypyridinoline, for use as biochemical markers of collagen degradation

The collagen crosslinks, pyridinoline and deoxypyridinoline, have been developed as urinary markers of bone resorption but, despite wide clinical application of the technique, comparatively little attention has been paid to the standardization of these compounds. In this study, pyridinoline and deoxypyridinoline have been purified from bone and converted completely to monochloride trihydrochloride salts. In addition to mass spectrometry and NMR spectroscopy, the purity of the isolated materials was assessed by microelemental analysis including the chloride counterions. These purified compounds were used to establish individual molar absorptivity values as primary standardization criteria for the two crosslinks. For pyridinoline in 0.1 mol/L HCl, epsilon at 295 nm was 5490 L mol(-1) cm(-1); in 50 mmol/L sodium phosphate, pH 7.5, epsilon at 325 nm was 5785. The corresponding values for deoxypyridinoline at acid and neutral pH were 5160 and 5290 L mol(-1) cm(-1). The availability of standardization criteria for the crosslinks will allow more meaningful comparisons of clinical data between different laboratories.

Standardization of pyridinium crosslinks, pyridinoline and deoxypyridinoline, for use as biochemical markers of collagen degradation

The collagen crosslinks, pyridinoline and deoxypyridinoline, have been developed as urinary markers of bone resorption but, despite wide clinical application of the technique, comparatively little attention has been paid to the standardization of these compounds. In this study, pyridinoline and deoxypyridinoline have been purified from bone and converted completely to monochloride trihydrochloride salts. In addition to mass spectrometry and NMR spectroscopy, the purity of the isolated materials was assessed by microelemental analysis including the chloride counterions. These purified compounds were used to establish individual molar absorptivity values as primary standardization criteria for the two crosslinks. For pyridinoline in 0.1 mol/L HCl, epsilon at 295 nm was 5490 L mol(-1) cm(-1); in 50 mmol/L sodium phosphate, pH 7.5, epsilon at 325 nm was 5785. The corresponding values for deoxypyridinoline at acid and neutral pH were 5160 and 5290 L mol(-1) cm(-1). The availability of standardization criteria for the crosslinks will allow more meaningful comparisons of clinical data between different laboratories.

Monoclonal antibody assay for free urinary pyridinium cross-links

The pyridinium cross-links of collagen, pyridinoline (Pyd) and deoxypyridinoline (Dpd), provide structural integrity and rigidity to collagen fibrils in bone. During bone degradation (resorption), the cross-links are released into the circulation and eventually excreted in urine. Pyridinium cross-link measurements in urine have been shown to be sensitive and specific indicators of resorption by both established HPLC and newer enzyme immunoassay (EIA) techniques. We have developed a monoclonal antibody that preferentially binds to the non-peptide-bound free forms of Pyd & Dpd. We have incorporated the antibody conjugated to alkaline phosphatase in a competitive EIA by using Pyd-coated microtiter strip wells. After a 3-h incubation of sample and antibody-enzyme conjugate, color is developed for 1 h with p-nitrophenyl phosphate as the substrate. The intraassay (n = 52) CVs were 3.0-7.6%, and interassay (n = 8) CVs were 6.1-7.4%. Comparisons of the assay (y) with HPLC (x) and a polyclonal antibody-based EIA (x') gave regression equations of y = 0.46x + 4, r = 0.96, and y = 0.56x' + 8, r = 0.96. The EIA detected increased Pyd & Dpd concentrations in urine from postmenopausal women and patients with osteoporosis, hyperthyroidism, hyperparathyroidism, and Paget disease of bone. EIA concentrations also reflected the reduction in Pyd&Dpd excretion resulting from estrogen replacement in surgically menopausal women. Measurement of pyridinium cross-links with this simple EIA appears to provide an accurate index of the rate of resorption and may be useful for metabolic bone disease assessment and monitoring the effects of antiresorptive therapy.

Monoclonal antibody assay for free urinary pyridinium cross-links

The pyridinium cross-links of collagen, pyridinoline (Pyd) and deoxypyridinoline (Dpd), provide structural integrity and rigidity to collagen fibrils in bone. During bone degradation (resorption), the cross-links are released into the circulation and eventually excreted in urine. Pyridinium cross-link measurements in urine have been shown to be sensitive and specific indicators of resorption by both established HPLC and newer enzyme immunoassay (EIA) techniques. We have developed a monoclonal antibody that preferentially binds to the non-peptide-bound free forms of Pyd & Dpd. We have incorporated the antibody conjugated to alkaline phosphatase in a competitive EIA by using Pyd-coated microtiter strip wells. After a 3-h incubation of sample and antibody-enzyme conjugate, color is developed for 1 h with p-nitrophenyl phosphate as the substrate. The intraassay (n = 52) CVs were 3.0-7.6%, and interassay (n = 8) CVs were 6.1-7.4%. Comparisons of the assay (y) with HPLC (x) and a polyclonal antibody-based EIA (x') gave regression equations of y = 0.46x + 4, r = 0.96, and y = 0.56x' + 8, r = 0.96. The EIA detected increased Pyd & Dpd concentrations in urine from postmenopausal women and patients with osteoporosis, hyperthyroidism, hyperparathyroidism, and Paget disease of bone. EIA concentrations also reflected the reduction in Pyd&Dpd excretion resulting from estrogen replacement in surgically menopausal women. Measurement of pyridinium cross-links with this simple EIA appears to provide an accurate index of the rate of resorption and may be useful for metabolic bone disease assessment and monitoring the effects of antiresorptive therapy.

A preliminary investigation into the aetiology of Meares-Irlen syndrome

A recent double-masked placebo-controlled trial has confirmed that some children experience a reduction in symptoms of eyestrain and headache when they read through individually prescribed coloured filters and has shown that this benefit cannot be solely attributed to a placebo effect. People who are helped by coloured filters in this way have been described as having "Meares-Irlen syndrome'. We investigated the mechanism of this benefit by studying the optometric and visual perceptual characteristics of the children in the double-masked study. This population had normal refractive errors and heterophorias (none of the subjects had strabismus). They demonstrated slightly, but significantly, reduced amplitudes of accommodation and vergence and poor stereo-acuity. However, these factors seemed to be correlates of Meares-Irlen syndrome rather than the underlying cause. Pattern glare, a sensitivity to striped patterns (e.g. lines of text), was prevalent in our sample and was significantly associated with the subjects' symptoms. The spatial contrast sensitivity function was normal.

New technique for studying incision depth in experimental radial keratotomy

Older techniques of analyzing incision depth in incisional keratotomy consist of serial transverse sections taken at various points along the incision. Information as to shape and depth of the incision are reconstructed from these sections. We describe a new method for studying the incision depth and profile along the entire incision length.

Coronary operations in patients with spinal cord injury

BACKGROUND

The risk of heart disease in patients with spinal cord injury is similar to that in the general population. The physiologic derangements raise special problems in patients with SCI having coronary operations.

METHODS

From January 1980 to May 1995, we performed coronary artery bypass procedures on 20 patients with SCI; 4 were tetraplegic and the remainder were paraplegic. The indication for operation was angina: unstable (13), exertional (4), or postinfarctional (3). Bowel and bladder care was given immediately before operation; operating room tables were double padded and a pelvic wrap was used to protect the back. Electric wheelchairs were used for early mobilization.

RESULTS

Vasomotor instability from cardiopulmonary bypass was not present in patients with SCI. Pharmacologic support was required in the operating room by 4 patients for low vascular resistance, but in only one case in the intensive care unit. One patient required ventilation support for more than 24 hours. All patients were able to cough effectively. No thoracic wound complications occurred. There were three operative deaths, all in patients with multiple risk factors. The acute hospital stay averaged 9.3 days; patients were then transferred to an SCI unit for rehabilitation, were upper-extremity weight bearing was restricted for 2 to 4 weeks.

CONCLUSIONS

Patients should not be denied coronary artery bypass procedures because of an SCI, but their special needs must be managed properly.

Consulting skills training and medical students' interviewing efficiency

In more traditional medical education, medical students took a patient's medical history by asking a series of sequenced, routine questions, covering presenting medical problem(s); medical history; social and personal history; systems review; and physical examination. Following this process, the student then attempted to derive the patient's medical problems. This inductive problem-solving paradigm may not assist students to prepare for their future interviewing needs, given doctors use a hypothetico-deductive, problem-solving approach when interviewing patients and numerous researchers have developed specialized communication skills training programmes designed to enhance students' interviewing skills. Students given specific consulting skills training have tended to show significantly greater interpersonal effectiveness and improved interview behaviours compared with students who experience traditional patient clerking training. These improvements in interviewing tend to persist over the period of students' medical training. The aim of the present study was to determine whether specialized communication skills training helped students elicit greater quantity and quality of information from patients and if so, whether such information assisted students in improving their diagnostic skills. Videotaped history-taking interviews conducted by students trained in communication skills and untrained (control) students were rated for their interview efficiency. A comparison of ratings given by experimentally naive, independent observers revealed that trained students were more efficient, but took no longer than their control group counterparts to elicit fuller, more relevant information. However, the student groups did not differ in the accuracy or scope of their medical diagnoses. It is argued that students' lack of medical knowledge in this early phase of their clinical training militated against their being able to use their interviewing competence to derive more potentially accurate medical diagnoses.

Dyslexia: the link with visual deficits

Some research reports suggest that visual anomalies may have a causative role in dyslexia, and on this basis certain forms of therapy have been proposed. Recently, we have published the initial results of a matched group study which found dyslexia to be associated with binocular instability, reduced amplitude of accommodation, and reduced contrast sensitivity for both low spatial frequencies and uniform field flicker. The binocular instability was best identified by measuring the vergence amplitude: a modified Dunlop test failed to differentiate reliably between the two groups. Here, we report a significant correlation between flicker threshold and binocular instability, thus linking sensory and motor visual correlates of dyslexia. We also present further new analyses on the interaction between optometric variables and the psychometric measurement of coding skills. The results of these analyses disagree with a recent claim that binocular vision anomalies might cause poor performance at coding tasks. Our studies indicate that visual characteristics are not the major aetiological factors in specific reading difficulty.

Optometric correlates of Meares-Irlen syndrome: a matched group study

People who report visual perceptual distortions, typically when reading, that are alleviated by using coloured filters are described as suffering from 'Meares-Irlen Syndrome'. A recent double-masked placebo-controlled trial showed that this condition cannot be solely explained as a placebo effect and that the beneficial filter is idiosyncratic and sometimes needs to be highly specific. Several mechanisms have been suggested for Meares-Irlen Syndrome including ocular motor (binocular and accommodative) anomalies, a sensitivity to patterned stimuli (pattern glare), and a deficit of the transient visual sub-system. We investigated these hypotheses by comparing 16 children, who reported the symptoms described above and who showed a sustained benefit from coloured filters, with 25 control children who came from the same school and were matched for age, reading performance and intelligence. The 'Meares-Irlen Syndrome' group had slightly, but significantly, reduced vergence and accommodative amplitudes and stereo-acuity; they also demonstrated significantly more pattern glare. The two groups did not differ significantly in their visual acuities, refractive error, dissociated or associated heterophoria, AC/A ratio, or ability to perceive 20 Hz flicker. It appears that certain ocular motor factors are correlates of Meares-Irlen Syndrome, rather than the primary underlying cause of the symptoms. The results support the hypothesis that pattern glare may be involved in the mechanism of Meares-Irlen Syndrome.

A new protocol for the optometric management of patients with reading difficulties

Research by Evans et al. (Ophthal. Physiol. Opt. 15, 481-487, 1995) has demonstrated a correlation between visual processing and ocular motor factors in people with specific reading difficulties (dyslexia). In addition, research by Wilkins et al. (Ophthal. Physiol. Opt. 14, 365-370, 1994) has shown that some people with dyslexia will benefit from a reduction of perceptual symptoms of discomfort and distortion if they use individually prescribed coloured filters. Three examples of the dyslexic patients who attend at the Institute of Optometry clearly demonstrate the importance of full investigation of ocular function, including the assessment of the effect of colour on visual perception. All three patients presented with similar symptoms of asthenopia when reading. Symptoms were alleviated for the first patient by use of orthoptic treatment of an exotropia with intermittent suppression. With the second patient, ocular motor functions were found to be within acceptable limits and relief of symptoms was obtained by the prescribing of lenses of a specific chromaticity. For the third patient, both orthoptic intervention and the use of specifically tinted lenses were necessary to relieve the visual difficulties that were being experienced. By taking advantage of recent research and developments in optometric instrumentation, it is possible for some of those with dyslexia to receive considerable benefit from optometric intervention.

Is there a visual deficit in dyslexia resulting from a lesion of the right posterior parietal lobe?

Dyslexia has conventionally been attributed to a left hemisphere deficit affecting language skills. However, it has recently been suggested that two-thirds of dyslexic people have a lesion of the right posterior parietal lobe (RPPL) resulting in poor oculo-motor control. It has been reported that neurological patients with RPPL lesions commonly manifest a neglect of the left side of space and this has also been described in clinical observations of 'visual dyslexics'. We investigated this hypothesis with a sample of 53 dyslexic children and 53 controls using a line-bisection task. In the horizontal test condition both groups tended to transect slightly to the left of the midpoint (mean displacement 0.14 mm for controls; 0.4 mm for dyslexics). The result suggests a small right side neglect which, contrary to one report in the literature, is found here in developmental dyslexics as well as controls, and leads to the conclusion that RPPL lesion is unlikely to be a common feature of dyslexia.

Effect of pattern glare and colored overlays on a stimulated-reading task in dyslexics and normal readers

Scotopic sensitivity syndrome or the Irlen syndrome describes symptoms of asthenopia anamolous visual performance experienced while reading that are lessened by colored filters. One putative explantation for this condition relates to pattern glare: a hypersensitivity to repetitive patterns, including lines of print on a page. Experiment 1 used a placebo-controlled paradigm to investigate the effect of pattern glare and colored overlays on performance at a simulated reading visual search task. Despite the fact that the subjects were university students, the results showed a tendency, of border-line significance, to support the conclusion that colored filters seem to improve reading through ameliorating pattern glare. In experiment 2 we compared the prevalence of pattern glare in matched groups of dyslexic children and good readers. The dyslexic group reported more pattern glare, but also reported more glare from a control stimulus. Pattern glare in the dyslexic group was directly correlated with flicker sensitivity. The results are related to recent research on visual processing and ocular-motor function in dyslexia.

Double-masked placebo-controlled trial of precision spectral filters in children who use coloured overlays

We selected 68 children who reported benefit from individually chosen sheets of coloured plastic placed upon the page when reading, and who used these regularly without prompting. These children viewed text illuminated by coloured light in an apparatus that allowed the separate manipulation of hue (colour) and saturation (depth of colour), at constant luminance. Many of the children reported improvements in perception when the light had a chromaticity within a limited range, which was different for each individual. A pair of plastic spectacle lenses ('experimental' lenses) was dyed so as to provide the appropriate chromaticity under conventional white (F3) fluorescent light. An additional pair was prepared having very similar colour but with a chromaticity outside the range in which perception was reported to improve ('control' lenses). Each pair was provided for 1 month in random order. The children kept diaries (36 completed) recording symptoms of eye-strain and headache. The children and those responsible for their assessment were unable reliably to distinguish 'experimental' from 'control' lenses. Nevertheless, symptoms were less frequent on days when the 'experimental' lenses were worn (P < 0.003).

Videokeratographic evaluation of peripheral redeepening in the cadaver eye

Radial incisions must be deep enough to correct myopia. As currently performed, most surgeons set their diamond blades at a constant depth and do not alter the blade length throughout the procedure. The cornea is not uniformly thick; the central cornea is the thinnest and it thickens toward the periphery. Therefore, an incision of constant depth would be deeper centrally and thinner peripherally. Peripheral redeepening of the cornea would in theory make the incision depth deeper throughout and should increase the effect of radial incisions. We reviewed the literature on this technique and performed radial incisional studies on the human cadaver eye using videokeratography to measure incision depth indirectly. Based on our studies, we believe that peripheral redeepening has no effect on central cornea flattening.

An investigation of some sensory and refractive visual factors in dyslexia

The role of visual factors in dyslexia has been a long-standing source of controversy. Recent research has suggested that there may be a deficit of the transient visual subsystem in dyslexia. The evidence for this hypothesis comes principally from investigations of spatial and temporal contrast sensitivity and visual persistence. This evidence is reviewed and it is noted that previous work has never applied two of these purported "tests of transient function" to the same subject group. The hypothesised transient system deficit in dyslexia was investigated in a study comparing 43 control with 39 dyslexic children who were matched for age, sex, and intelligence. Comprehensive psychometric and optometric data were obtained, including visual acuities and refractive errors. The spatial contrast sensitivity function was determined in such a way as to investigate further the findings of Lovegrove, Martin, Bowling, Blackwood, Badcock and Paxton [(1982) Neuropsychology, 20, 309-315] and Martin and Lovegrove [(1984) Neuropsychologia, 22, 73-77]. It might be expected, from the work of Merigan and Maunsell [(1990) Neuroscience, 5, 347-352], that a better test of magno-cellular function would be to investigate the modulation threshold for a virtually uniform field that was flickering sinusoidally at 10 Hz. This temporal contrast sensitivity was studied in a similar way to Brannan and Williams [(1988) Clinical Vision Sciences, 3, 137-142]. A non-verbal simulated reading visual search task was used to investigate the effect of any visual deficits on a test that was, in its low-level visual requirements, similar to reading. The following factors were found to be significantly associated with dyslexia: reduced visual acuity, impaired flicker detection at 10 Hz, reduced low spatial frequency contrast sensitivity, and slightly slower performance at a simulated reading visual search task. The two alleged "tests of transient function" were only weakly correlated with one another (r = 0.183), suggesting that these variables do not measure the same function. Much of the dyslexic group's slightly slower performance at the simulated reading task could be accounted for by the psychometric variable of visual sequential memory. Like reading, the simulated reading task requires the accurate perception of sequential characters. Hence, it seems unlikely that the low-level visual deficits in the dyslexic group were major causes of their poor reading performance. Alternative explanations for the results are discussed.

Functional characteristics of small placental arteries

OBJECTIVES

The aim of this study was to investigate characteristics of placental arteries capable of influencing vasomotor tone in the fetoplacental vascular bed. Contractile characteristics and endothelium-dependent and endothelium-independent relaxation were examined.

STUDY DESIGN

By means of a small vessel myograph arteries of mean normalized internal diameter 353.22 +/- 13.14 microns were studied under isometric conditions. Contractile function was assessed with a variety of agonists, including angiotensin II, endothelin-1, the thromboxane mimetic U46619, prostaglandin E2, and prostaglandin F2 alpha. The effect of physiologic and supraphysiologic PO2 on vascular function was also examined. Relaxation was assessed in response to known endothelium-dependent vasodilators, including acetylcholine, bradykinin, histamine, and A23187 and to sodium nitroprusside (endothelium independent). The effect of indomethacin and the nitric oxide synthase inhibitor, NG-nitro-L-arginine methyl ester on contractile function was also evaluated.

RESULTS

Sensitivity to sodium nitroprusside was reduced by a high PO2. U46619 was the most potent constrictor agonist studied. The response of precontracted arteries to known endothelium-dependent vasodilators was minimal, other than for histamine, which led to modest relaxation. The constrictor response to U46619 was increased in the presence of NG-nitro-L-arginine methyl ester.

CONCLUSIONS

Oxygen tension may be an important determinant of relaxation in small placental arteries. Receptor-mediated release of endothelium-derived relaxing factor is not a major mechanism in the fetoplacental circulation.

Investigation of accommodative and binocular function in dyslexia

The visual correlates of dyslexia are the subject of controversy, and much evidence suggests that they may include some aspects of binocular and accommodative function. These factors were investigated in 43 control and 39 dyslexic children, who were matched for age, sex and performance intelligence quotient. The dyslexic group exhibited significantly lower positive and negative vergence reserves, and vergence instability when the eyes were dissociated at near. Their amplitudes of accommodation also were significantly reduced. However, other measures including dissociated and associated heterophoria and accommodative lag and facility were similar in both groups. The stability of motor ocular dominance, as assessed with a modified Dunlop test, was similar in both groups. The results of a simulated reading visual search task suggested that the vergence and accommodative dysfunction were not a major cause of the dyslexia. Further analyses, using reading-age matched groups, suggested that these ocular motor correlates were not attributable to the better reading performance in the control group. The most likely remaining explanation is that they are, in most cases, non-causal correlates of the dyslexia.

Behavioural assessment of the effectiveness of a communication programme for medical students

This study evaluated the effectiveness of a communication programme taught to medical students at the University of Melbourne in their preclinical years. The effectiveness of the programme was assessed by comparing videotaped history-taking interviews completed by a cohort of first-year clinical students in 1986, who had not undertaken the communication programme, with a similar cohort of first-year clinical students in 1992 who had undertaken the programme. The students from the 1986 cohort who had not undertaken communication training in their preclinical course completed their videotaped interviews as part of the experimental evaluation of a consulting skills training programme carried out in 1986-87. A comparison of ratings given by two experimentally naive, independent observers revealed that the 1992 student cohort demonstrated some significantly better skills at questioning and facilitating communication with patients. By contrast, the 1986 student cohort showed significantly greater skills at maintaining relevance in their interviews and greater capacity to explore patients' psychosocial concerns. These data suggest that students acquire the most effective interview skills when interacting with patients during their clinical training.

Measuring medical students' empathy skills

Empathy is an important skill for the medical practitioner or medical students to develop when interviewing patients. It helps the interviewer establish effective communication, which is important for accurate diagnosis and patient management. Two facets of medical education limit students' development of accurate empathy: the traditional format of interviewing training and the social ethos of medical training and medical practice, which stress clinical detachment. A number of researchers and educators have developed consulting skills training programmes, designed to enhance students' empathic skills and ability. One difficulty for researchers has been the conceptual complexity of the term 'empathy' and greater difficulty in measuring the dimension. This paper reviews the range of approaches to the measurement of empathy and reports on a research study designed to evaluate a two-stage measurement technique, involving a pencil-and-paper test of empathy and independent observer ratings of medical students' actual interview behaviours. Results lead to the conclusion that pencil-and-paper tests of empathy cannot incorporate the range of complex cognitive, emotional and behavioural components of the empathy construct. On the other hand, trained observers have been able to use items on a specially developed History-taking Rating Scale to discriminate between the empathic behaviours of a group of students trained in consulting skills with those of a group of control students who each carried out videotaped history-taking interviews with hospitalized patients.

Neuropathology of the chronic epileptic syndrome induced by intrahippocampal tetanus toxin in rat: preservation of pyramidal cells and incidence of dark cells

A few nanograms of tetanus toxin injected into a rat hippocampus causes a chronic epileptic syndrome characterized by brief seizures that recur intermittently for about 6 weeks. Cognitive and other behavioural impairments persist after the seizures and other epileptic electrographic activity have remitted, and may be permanent. Our previous studies suggested that the behavioural changes following seizure remission were an indication of functional impairment associated with decreased neuronal excitability rather than with neuronal loss. The conclusion that neurons were preserved relied on qualitative histological observations and, indirectly, on electrophysiological measurements of the amplitudes of antidromic population spikes. Recently, gross histopathology has been described in a quantitative histological study of rats 7-10 days after they had received rather higher doses of intrahippocampal tetanus toxin. Here we report a quantitative histological study of hippocampi from rats which had gained remission from seizures induced by low doses of tetanus toxin. Adult Sprague Dawley rats received unilateral injections of 3-4 ng (about 6-8 mouse LD50) tetanus toxin, or vehicle, into the dorsal hippocampus. The first experiment confirmed that postsynaptic evoked responses recorded from pyramidal cells were depressed 10-19 weeks after injection. Unexpectedly, there also was a decrease of 20% in the antidromic response from CA3a contralateral to the injection. However, cell counts in these hippocampi revealed no change in pyramidal cell numbers. The second experiment used rats from two breeding colonies, prepared for histology 7 weeks after injection. Hippocampal pyramidal cell numbers were within the normal range in all but three of the 24 rats that had received tetanus toxin. These three had lesions of the CA1 pyramidal layer contralateral to the injection. The lesions were of the order of 2 mm in diameter, and were associated with glial proliferation. When these three cases were excluded, there remained a small increase in glial density in CA1 of the toxin-injected rats. In addition, toxin-injected rats from one of the colonies were susceptible to a pathology known as acidophylic or dark cell change. These occurred in 11 of 18 toxin-injected rats from this colony, in all divisions of the pyramidal layer, in both the injected and the contralateral hippocampus (where parallel studies revealed independent secondary epileptic foci). We conclude that loss of pyramidal neurons is not necessary for the persistent behavioural changes in this model.(ABSTRACT TRUNCATED AT 400 WORDS)

Tinted lenses and related therapies for learning disabilities--a review

Research relating to the use of Irlen tinted lenses and coloured overlays for underachievers is reviewed. Many of the studies were not published in refereed journals and were methodologically poor. The weaknesses of the Irlen argument are discussed, including the absence of evidence to support the claims that these tints need to be uniquely prescribed and manufactured. Syntonics is another form of visual colour therapy that has been applied to those with a learning disability. Research on this is reviewed, and is also shown to have procedural irregularities which preclude firm conclusions. Owing to the poor quality of much of this research the claims of the protagonists of these therapies cannot be proved or disproved. A proposed new therapy is normally preceded by a valid theoretical hypothesis; this has been lacking in the present topic. Recently, a feasible explanation has been proposed in terms of 'pattern glare' resulting from mild hypersensitivity to epileptogenic patterns. This, together with potential alternative theories, is discussed. In the conclusion of this review, advice is given for eye-care practitioners who may be consulted on these therapies.

Review of ophthalmic factors in dyslexia

Dyslexia and the effect of visual problems on reading ability have long been subjects of controversy. This paper critically reviews the literature on the relationship between reading disability and visual acuity, refractive error, binocular vision anomalies, eye movements, ocular pathology and the transient and sustained visual systems. The limitations of much of the work in this field are described, with particular reference to the problems of subject selection and group matching. Tentative conclusions, with deference to the complex nature of dyslexia, are drawn and suggestions are made for future research.

Serum lipoperoxidation products in an infant with hemolytic-uremic syndrome

We detected increased concentrations of lipoperoxidation products, as malondialdehyde, in the serum of an infant with classic hemolytic-uremic syndrome. The concentrations declined when peritoneal dialysis was initiated and eventually returned to normal after clinical recovery. Our observation adds to the existing body of evidence that links the pathogenesis of hemolytic-uremic syndrome to peroxidative damage and to the rationale for using antioxidant agents as part of the therapy for this disease process.

Serum lipoperoxidation products in an infant with hemolytic-uremic syndrome

We detected increased concentrations of lipoperoxidation products, as malondialdehyde, in the serum of an infant with classic hemolytic-uremic syndrome. The concentrations declined when peritoneal dialysis was initiated and eventually returned to normal after clinical recovery. Our observation adds to the existing body of evidence that links the pathogenesis of hemolytic-uremic syndrome to peroxidative damage and to the rationale for using antioxidant agents as part of the therapy for this disease process.

Scores on the Interpersonal Reactivity Index: a sample of Australian medical students

Scores of a sample of 113 Australian medical students on the Interpersonal Reactivity Index are compared with the normative data. The comparison suggests that these medical students' scores are generally comparable. A comparison of 4th and 6th Year clinical students indicated few differences between these samples, the exception being the subscale “Fantasy” on which 6th Year women students scored significantly higher than the other three student samples. These data will be used in a longitudinal study of consulting skills training given to the 4th Year students.