Evolutionary design of explainable algorithms for biomedical image segmentation

An unresolved issue in contemporary biomedicine is the overwhelming number and diversity of complex images that require annotation, analysis and interpretation. Recent advances in Deep Learning have revolutionized the field of computer vision, creating algorithms that compete with human experts in image segmentation tasks. However, these frameworks require large human-annotated datasets for training and the resulting "black box" models are difficult to interpret. In this study, we introduce Kartezio, a modular Cartesian Genetic Programming-based computational strategy that generates fully transparent and easily interpretable image processing pipelines by iteratively assembling and parameterizing computer vision functions. The pipelines thus generated exhibit comparable precision to state-of-the-art Deep Learning approaches on instance segmentation tasks, while requiring drastically smaller training datasets. This Few-Shot Learning method confers tremendous flexibility, speed, and functionality to this approach. We then deploy Kartezio to solve a series of semantic and instance segmentation problems, and demonstrate its utility across diverse images ranging from multiplexed tissue histopathology images to high resolution microscopy images. While the flexibility, robustness and practical utility of Kartezio make this fully explicable evolutionary designer a potential game-changer in the field of biomedical image processing, Kartezio remains complementary and potentially auxiliary to mainstream Deep Learning approaches.

Resisting T cell attack: tumor-cell-intrinsic defense and reparation mechanisms

Cytotoxic T lymphocytes (CTLs) are antigen-specific killer cells equipped to identify and eliminate host cells that have been altered through infection or transformation. Both chimeric antigen-receptor (CAR) T cell therapies and immune checkpoint blockade (ICB) therapies are based on successful elimination of tumor cells by cytotoxic effectors. In this opinion article, we outline cell-intrinsic mechanisms by which tumor cells defend against CTLs, highlighting pathways that confer resistance and proposing opportunities for combination therapies. We discuss how exogenous killing entities [e.g., supramolecular attack particles (SMAPs)] offer a novel strategy to circumvent cellular resistance mechanisms. Our opinion article highlights the importance of identifying, quantifying, and targeting tumor defense mechanisms at the interface between tumor cells and CTLs as a critical consideration in the development of immunotherapy approaches.

Greek Fire, Poison Arrows, and Scorpion Bombs: How Tumor Cells Defend Against the Siege Weapons of Cytotoxic T Lymphocytes

CD8⁺ cytotoxic T lymphocytes (CTLs) are the main cellular effectors of the adaptive immune response against cancer cells, which in turn have evolved sophisticated cellular defense mechanisms to withstand CTL attack. Herein we provide a critical review of the pertinent literature on early and late attack/defense events taking place at the CTL/target cell lytic synapse. We examine the earliest steps of CTL-mediated cytotoxicity (“the poison arrows”) elicited within seconds of CTL/target cell encounter, which face commensurately rapid synaptic repair mechanisms on the tumor cell side, providing the first formidable barrier to CTL attack. We examine how breach of this first defensive barrier unleashes the inextinguishable “Greek fire” in the form of granzymes whose broad cytotoxic potential is linked to activation of cell death executioners, injury of vital organelles, and destruction of intracellular homeostasis. Herein tumor cells deploy slower but no less sophisticated defensive mechanisms in the form of enhanced autophagy, increased reparative capacity, and dysregulation of cell death pathways. We discuss how the newly discovered supra-molecular attack particles (SMAPs, the “scorpion bombs”), seek to overcome the robust defensive mechanisms that confer tumor cell resistance. Finally, we discuss the implications of the aforementioned attack/defense mechanisms on the induction of regulated cell death (RCD), and how different contemporary RCD modalities (including apoptosis, pyroptosis, and ferroptosis) may have profound implications for immunotherapy. Thus, we propose that understanding and targeting multiple steps of the attack/defense process will be instrumental to enhance the efficacy of CTL anti-tumor activity and meet the outstanding challenges in clinical immunotherapy.

Ultrarapid lytic granule release from CTLs activates Ca2+-dependent synaptic resistance pathways in melanoma cells

Human cytotoxic T lymphocytes (CTLs) exhibit ultrarapid lytic granule secretion, but whether melanoma cells mobilize defense mechanisms with commensurate rapidity remains unknown. We used single-cell time-lapse microscopy to offer high spatiotemporal resolution analyses of subcellular events in melanoma cells upon CTL attack. Target cell perforation initiated an intracellular Ca²⁺ wave that propagated outward from the synapse within milliseconds and triggered lysosomal mobilization to the synapse, facilitating membrane repair and conferring resistance to CTL induced cytotoxicity. Inhibition of Ca²⁺ flux and silencing of synaptotagmin VII limited synaptic lysosomal exposure and enhanced cytotoxicity. Multiplexed immunohistochemistry of patient melanoma nodules combined with automated image analysis showed that melanoma cells facing CD8⁺ CTLs in the tumor periphery or peritumoral area exhibited significant lysosomal enrichment. Our results identified synaptic Ca²⁺ entry as the definitive trigger for lysosomal deployment to the synapse upon CTL attack and highlighted an unpredicted defensive topology of lysosome distribution in melanoma nodules.

IL-17+ Mast Cell/T Helper Cell Axis in the Early Stages of Acne

Acne is a multifactorial disease driven by physiological changes occurring during puberty in the pilosebaceous unit (PSU) that leads to sebum overproduction and a dysbiosis involving notably Cutibacterium acnes. These changes in the PSU microenvironment lead to a shift from a homeostatic to an inflammatory state. Indeed, immunohistochemical analyses have revealed that inflammation and lymphocyte infiltration can be detected even in the infraclinical acneic stages, highlighting the importance of the early stages of the disease. In this study, we utilized a robust multi-pronged approach that included flow cytometry, confocal microscopy, and bioinformatics to comprehensively characterize the evolution of the infiltrating and resident immune cell populations in acneic lesions, beginning in the early stages of their development. Using a discovery cohort of 15 patients, we demonstrated that the composition of immune cell infiltrate is highly dynamic in nature, with the relative abundance of different cell types changing significantly as a function of clinical lesion stage. Within the stages examined, we identified a large population of CD69⁺ CD4⁺ T cells, several populations of activated antigen presenting cells, and activated mast cells producing IL-17. IL-17⁺ mast cells were preferentially located in CD4⁺ T cell rich areas and we showed that activated CD4⁺ T cells license mast cells to produce IL-17. Our study reveals that mast cells are the main IL-17 producers in the early stage of acne, underlying the importance of targeting the IL-17⁺ mast cell/T helper cell axis in therapeutic approaches.

Live or let die: Pyroptosis and inflammasome activation in glial cells during multiple sclerosis and experimental autoimmune encephalomyelitis

Inflammasome-associated caspases mediate the maturation and release of the proinflammatory cytokines IL-1β and IL-18, and activate the pore-forming protein gasdermin-D (GSDMD). Recently, GSDMD was shown to be the primary executioner of pyroptosis, a lytic form of programmed cell death. Excessive GSDMD pore formation causes local osmotic swelling and eventual membrane lysis. Although evidence has emerged for inflammasome activation and pyroptosis in neurological diseases, the role of GSDMD in neuroinflammation remains uncharacterized. Multiple sclerosis (MS) is the prototypic inflammatory demyelinating disease of the central nervous system (CNS). We provide molecular evidence for GSDMD-mediated inflammasome activation and pyroptosis in both macrophages/microglia and, unexpectedly, in myelin-forming oligodendrocytes (ODCs) in the CNS of patients with MS and in the associated animal model, experimental autoimmune encephalomyelitis (EAE). We observe inflammasome activation, GSDMD expression, and pyroptosis in human microglia and ODCs in vitro inflammatory stimulation. Further, we demonstrate that both caspase-1 inhibition by the small molecule inhibitor VX-765 and GSDMD inhibition via siRNAs suppress pyroptosis in human microglia. VX-765 treatment of EAE animals reduced expression of inflammasome- and pyroptosis-associated proteins in the CNS, reduced neuroinflammation, prevented axonal injury, and improved neurobehavioral performance. Thus, GSDMD-mediated pyroptosis in multiple glial populations represents a previously unrecognized mechanism of inflammatory demyelination and represents a unique therapeutic opportunity for mitigating neuroinflammation.

M011L-deficient oncolytic myxoma virus induces apoptosis in brain tumor-initiating cells and enhances survival in a novel immunocompetent mouse model of glioblastoma

BACKGROUND

Myxoma virus (MYXV) is a promising oncolytic agent and is highly effective against immortalized glioma cells but less effective against brain tumor initiating cells (BTICs), which are believed to mediate glioma development/recurrence. MYXV encodes various proteins to attenuate host cell apoptosis, including an antiapoptotic Bcl-2 homologue known as M011L. Such proteins may limit the ability of MYXV to kill BTICs, which have heightened resistance to apoptosis. We hypothesized that infecting BTICs with an M011L-deficient MYXV construct would overcome BTIC resistance to MYXV.

METHODS

We used patient-derived BTICs to evaluate the efficacy of M011L knockout virus (vMyx-M011L-KO) versus wild-type MYXV (vMyx-WT) and characterized the mechanism of virus-induced cell death in vitro. To extend our findings in a novel immunocompetent animal model, we derived, cultured, and characterized a C57Bl/6J murine BTIC (mBTIC0309) from a spontaneous murine glioma and evaluated vMyx-M011L-KO efficacy with and without temozolomide (TMZ) in mBTIC0309-bearing mice.

RESULTS

We demonstrated that vMyx-M011L-KO induces apoptosis in BTICs, dramatically increasing sensitivity to the virus. vMyx-WT failed to induce apoptosis as M011L protein prevented Bax activation and cytochrome c release. In vivo, intracranial implantation of mBTIC0309 generated tumors that closely recapitulated the pathological and molecular profile of human gliomas. Treatment of tumor-bearing mice with vMyx-M011L-KO significantly prolonged survival in immunocompetent-but not immunodeficient-mouse models, an effect that is significantly enhanced in combination with TMZ.

CONCLUSIONS

Our data suggest that vMyx-M011L-KO is an effective, well-tolerated, proapoptotic oncolytic virus and a strong candidate for clinical translation.

New method for assessing hand disinfection shows that pre-operative alcohol/chlorhexidine rub is as effective as a traditional surgical scrub

BACKGROUND

Several studies have shown that rubbing hands with an alcohol/chlorhexidine solution provides equivalent microbial decontamination to a conventional surgical scrub using aqueous chlorhexidine. However, the authors believe that these studies have methodological flaws that limit their applicability to the operating theatre environment. As such, a method was developed to compare products in an everyday operating theatre environment using working operating theatre personnel.

AIM

To determine whether or not an alcohol/chlorhexidine rub is as efficacious as a traditional surgical scrub using a novel method.

METHODS

Bacterial counts at baseline were collected from 20 anaesthetists using the glove juice method. Subsequently, with sequential exchange of sterile gloves, one hand underwent a 3-min scrub using 4% aqueous chlorhexidine, and the other hand underwent a 60-s rub with a 70% isopropyl alcohol/0.5% chlorhexidine solution. The residual bacterial count was collected for each hand after 30 min using the glove juice method. These counts were converted to log10 values to compare the baseline counts of right and left hands, and efficacy between the treatment groups.

FINDINGS

Mean [± standard deviation (SD)] bacterial counts at baseline were (log10) 4.42 ± 0.81 for left hands and 4.64 ± 0.60 for right hands (P > 0.05). The mean (± SD) reduction from baseline was (log10) 1.45 ± 0.50 for 4% chlorhexidine and 2.01 ± 0.98 for alcohol/chlorhexidine (P > 0.05).

CONCLUSION

An alcohol/chlorhexidine hand rub was found to be as efficacious as a traditional scrub after 30 min; this study differs from previous work as it was undertaken in a population of practising anaesthetists in their working environment. The McKenzie method allows baseline and study evaluations to be performed contemporaneously on the same individual. Each subject was his/her own control. This method offers a more clinically relevant way to compare disinfectant solutions than standard methods.

Sudden Infant Death Due to Truncus Arteriosus Communis Persistens with Mitral Valve Atresia and Left Ventricular Hypoplasia

Truncus arteriosus is a rare congenital heart defect characterized by a single common arterial trunk giving rise to both the pulmonary and systemic arteries. Concurrent cardiac abnormalities are common. In the absence of surgical intervention, the condition is associated with extremely high infant mortality, with the mechanism of death being either arrhythmia or congestive heart failure. We report the case of a previously healthy and reportedly normal two-week-old infant who was found dead in his crib. At autopsy he was found to have truncus arteriosus communis persistens, a rare subtype of truncus arteriosus with associated valve atresia and left ventricular hypoplasia. This case highlights that forensic pathologists may encounter severe cardiac malformations in previously normal infants, and the necessity for thorough evaluation and accurate diagnoses.

Design and manufacture of a novel system to simulate the biomechanics of basic and pitching shoulder motion

Objectives

Cadaveric models of the shoulder evaluate discrete motion segments using the glenohumeral joint in isolation over a defined trajectory. The aim of this study was to design, manufacture and validate a robotic system to accurately create three-dimensional movement of the upper body and capture it using high-speed motion cameras.

Methods

In particular, we intended to use the robotic system to simulate the normal throwing motion in an intact cadaver. The robotic system consists of a lower frame (to move the torso) and an upper frame (to move an arm) using seven actuators. The actuators accurately reproduced planned trajectories. The marker setup used for motion capture was able to determine the six degrees of freedom of all involved joints during the planned motion of the end effector.

Results

The testing system demonstrated high precision and accuracy based on the expected versus observed displacements of individual axes. The maximum coefficient of variation for displacement of unloaded axes was less than 0.5% for all axes. The expected and observed actual displacements had a high level of correlation with coefficients of determination of 1.0 for all axes.

Conclusions

Given that this system can accurately simulate and track simple and complex motion, there is a new opportunity to study kinematics of the shoulder under normal and pathological conditions in a cadaveric shoulder model.

Abstract LB-140: Targeting brain tumour initiating cells using a dual-pronged approach of oncolytic virotherapy and chemotherapeutics

BACKGROUND: Brain tumour initiating cells (BTICs) are stem-like cells hypothesized to mediate tumorigenesis and recurrence in glioblastoma multiforme (GBM). Patient-derived BTICs represent highly relevant preclinical GBM models, forming aggressive, infiltrative tumours in nude mice that closely recapitulate the phenotypic heterogeneity of patient GBMs. BTICs have also been shown to possess mechanisms mediating both chemo- and radio-resistance. Recently, success has been demonstrated in treating BTICs with oncolytic virotherapy (OV), which uses replication-competent viruses to specifically target and kill malignant cells. Myxoma virus (MyxV) is a promising oncolytic candidate, which our lab has shown to be highly efficacious in preclinical GBM models, effectively curing GBM xenografts with a single intra-cranial injection. By contrast, long-term survival is not obtained in MyxV-treated, BTIC-tumour-bearing mice, though survival is prolonged. HYPOTHESIS: We hypothesize that MyxV treatment of BTICs can be improved by utilizing clinically relevant chemotherapeutics identified via high-throughput pharmacoviral screens. RESULTS: We utilized a diverse, comprehensive panel of 80 small molecule inhibitors with preclinical and clinical anti-cancer efficacy to screen for synergy with MyxV treatment in vitro. Multiple candidates have been identified and are currently being validated for synergy (Chou-Talalay method) using a panel of genetically distinct, patient-derived BTICs. Our results implicate multiple potential targets for OV combination therapy, including topoisomerase I and the PI-3K/Akt/mTOR pathway. Target validation is currently underway using shRNA knockdowns and additional targeted inhibitors of these pathways. Further, the mechanism of synergistic cell death during these combination treatments is being explored. In vivo experiments utilizing the dual-pronged pharmacoviral approach are also underway. SIGNIFICANCE: We describe the nature and identity of compounds that carry the potential to sensitize BTICs to MyxV infection. Our findings offer an effective avenue to elucidate resistance mechanisms and develop efficacious combination therapies for targeting disease reservoirs within highly refractory GBMs.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr LB-140. doi:1538-7445.AM2012-LB-140

Lethal Neurotoxicity Induced by Endosulfan Ingestion

Endosulfan is a highly toxic agricultural pesticide that has been banned in many countries due to its significant neurotoxicity and environmental persistence. Accidental or intentional ingestion by humans induces severe neurological symptoms, which frequently culminate in coma or death. Forensic evaluation of suspected endosulfan toxicity cases can be challenging, given that endosulfan residue may not be detectable in the blood or tissues at the time of death. As such, evaluation of the case history in the context of the reported literature becomes extremely important. Although acute endosulfan toxicity in adults has been well documented, pediatric cases are rare within the literature. Here we present the case of a toddler who accidentally ingested an unknown quantity of endosulfan from an unmarked water bottle on his family farm. The child developed rapid-onset neurological symptoms, including vomiting and seizures, followed by coma. Despite medical intervention, the child was eventually pronounced brain dead and taken off life support. Autopsy revealed massive cerebral edema and its sequelae (sutural diastasis, pituitary necrosis, and dural venous thromboses), and pulmonary thromboemboli. Endosulfan was detected in the bottle from which the child drank. As endosulfan was not detectable in postmortem blood, the cause of death was certified based upon the totality of available information including history, consistency of the case history with the clinical presentation, and the autopsy findings.

Infantile Ischemic Occipital Scalp Ulcers May Mimic Impact Sites

The clinical or forensic pathologic evaluation of an infant with an apparently inflicted head injury can be challenging, particularly when objective findings are limited to the classic triad ascribed to “Shaken Baby Syndrome” – subdural and retinal hemorrhages and anoxic brain injury. These three findings together, in the absence of an apparent impact site (scalp or skull injury) have a controversial differential diagnosis. However, the discovery of an impact site of virtually any size is sufficient for some forensic pathologists to make the diagnosis of homicidal (impact) blunt head trauma in babies with limited additional evidence of abuse, or with the classic triad, but without careful consideration of its differential diagnosis. Although relatively uncommon in modern intensive care units, occipital scalp ulcers can and do occur, and may mimic the appearance of a blunt impact site. Two separate cases of infant death are presented to illustrate the nature and appearance of occipital pressure ulcers. Abnormalities of the occipital scalp were not detected in either infant upon hospital admission, but scalp lesions were clearly observed at autopsy. Macroscopically, these lesions closely resembled blunt impact sites. They were determined to be pressure ulcers based predominantly on the histologic findings of epidermal thinning and dermal homogenization, combined with the absence of both hemorrhage and stainable free iron. Further supportive factors were the absence of skull fractures, intracranial hemorrhages, and cerebrocortical contusions.

Evaluating the benefits and risks of neutering dogs and cats

Abstract

Neutering consists of removing the source of the hormones that control reproduction and determine secondary sexual characteristics. In dogs and cats, this is most commonly accomplished by castration or ovariectomy. While the primary purpose of neutering is to prevent reproduction, the procedure may have other physical and behavioural effects. Epidemiologic research has identified many beneficial and harmful outcomes associated with neutering. A definitively causal relationship between these outcomes and neuter status cannot be accepted without consistent evidence from multiple studies of adequate size and quality. However, consideration of the possible health consequences of these associations is warranted when offering owners recommendations concerning neutering. An evidence-based decision about neutering a particular pet requires integrating relevant research data with the veterinarian's clinical expertise and the needs and circumstances of the patient and owner. It is impossible to precisely predict the outcome of neutering for any individual. However, existing research does allow some generalization about the magnitude and clinical importance of specific risks and benefits. Overall, it appears justified to recommend spaying all females not intended for breeding, because the procedure is more likely to prevent rather than cause disease. In male dogs, the benefits of castration are not so clearly greater than the risks. The evidence is also mixed regarding the risks and benefits of neutering dogs before 5-6 months of age, and so no strong recommendation for or against the practice can be made. However, it is clear that spaying female dogs before their first heat is preferable to spaying them later.

Community based physiotherapy services in the Kivalliq Region of Nunavut, Canada

OBJECTIVES

Community based physiotherapy services are an integral component of the recent implementation of a medical rehabilitation program in the Kivalliq Region of Nunavut. Since the year 2000, the Inuit people of Canada's central Arctic have had direct access to physiotherapy in their home communities.

STUDY DESIGN

A quantitative review of physiotherapy services from January 1, 2001 to December 31, 2002.

METHODS

Workload measurement data gathered by the physiotherapists in the field will be utilized to present information on referral sources, location of services provided, client diagnoses and average duration of treatment provided. Administrative data will provide information on staffing complements and challenges to date. The need for physiotherapy referrals out of the Kivalliq Region will be reviewed.

RESULTS

Referral sources to physiotherapy services are varied, the majority of diagnoses are musculoskeletal in nature, followed by neurological and cardiovascular. Recruitment of the physiotherapy positions has been successful to date. Referrals out of the region for physiotherapy services have been rare since community based services have begun.

CONCLUSIONS

Access to physiotherapy services by the residents of the Kivalliq Region has been significantly enhanced since the implementation of the medical rehabilitation program.

The Millennium Dome "Watercycle" experiment: to evaluate water efficiency and customer perception at a recycling scheme for 6 million visitors

Thames Water's "Watercycle" project at the Millennium Dome was one of the largest in-building recycling schemes in Europe, designed to supply up to 500 m3/d of reclaimed water for WC and urinal flushing. It catered for over 6 million visitors in the year 2000. Overall, 55% of the water demand at the Dome was met by reclaimed water. The site was also one of the most comprehensive studies ever carried out of water conservation in a public environment, evaluating a range of water efficient appliances and researching visitor perceptions of reclaimed water. Within the Dome there were six identical core buildings housing the washrooms, which were equipped with a variety of different water-efficient devices for comparison. Water usage by the different appliances was monitored using a sophisticated metering and telemetry system. The importance of correct installation and maintenance of "high tech" water efficient devices was highlighted during the research programme, as some water wastage occurred due to poor installation. The results prove that metering should complement any large-scale water efficient system, so that any faults with the appliances can be quickly identified. The visitor survey showed very positive attitudes to the use of reclaimed water for non-potable uses.

Do anaesthetized patients recover better after Bispectral Index Monitoring?

Could Bispectral Index (BIS) monitoring during anaesthesia improve the recovery characteristics of patients? Previous studies have shown conflicting results. To eliminate bias, a control group of 75 cases anaesthetized by the authors was compared to a reference group of 141 cases anaesthetized by other anaesthetists. A study group of 71 cases was then anaesthetized by the authors titrating to BIS 40-50 and this was compared with the control group. Recovery characteristics were assessed using a Modified Aldrete score. BIS monitored cases had improvements in blood pressure stability (P = 0.023) and respiratory score (P = 0.016) throughout the study period. Activity and consciousness levels were higher on arrival in PACU in the BIS monitored group (P = 0.015 and P = 0.017) but were not maintained. There was no significant difference in mean oxygen saturation scores. The improved recovery characteristics in BIS monitored patients may have positive implications for safety, nursing workload, staffing, and cost savings in the PACU.

How do children who are clumsy remember modelled movements?

The ability of children who are clumsy, and of control children, to reproduce short sequences of simple movements immediately, and after a delay of 15 seconds, was examined. Four kinds of interference were introduced during the delay. These were visual or kinaesthetic each with either a high or a low spatial component. The reproductions of the movements by clumsy children were inferior to those by control children only after visual interference with a high spatial involvement. It was concluded that the memory of clumsy children for modelled movements is more dependent on visuospatial rehearsal than is the memory of normal children.

Race, socioeconomic status, and the subjective well-being of older Americans

Causal examination of factors influencing life satisfaction among older Americans can provide knowledge important to social policy development. Using rotated factor analysis, this study isolates two dimensions of life satisfaction, labeled happiness and morale, using data from the 1981 Harris survey on aging. Race, SES characteristics, and the two intervening variables of self-assessed health status and problems experienced are tested through path analysis on the two attributes of life satisfaction. Most of the effects of race and SES are mediated by self-assessed health status and problems experienced, and these two intervening variables are the strongest direct predictors of happiness and morale. Of particular significance are results which demonstrate that racial background has a strong influence on problems experienced, and that education is more influential than income on the life satisfaction factors tested in this study.

Sensitivity of cultured skin fibroblasts from patients with neurofibromatosis to DNA-damaging agents

Neurofibromatosis (NF) is an autosomal dominant disorder associated with various constitutional abnormalities as well as a striking predisposition for malignant and nonmalignant neoplasms, both in cells originating in and not originating in the neural crest. We have examined the sensitivity of cultured skin fibroblasts from patients with neurofibromatosis to several types of DNA damage. Fibroblasts in Dulbecco's modified Eagle's medium were plated at 10(2) to 2 X 10(4) cells per 75 cm2 tissue culture plates, and exposed to various doses of gamma radiation (leads to DNA scission), actinomycin D (a DNA intercalating agent), or mitomycin C (a bifunctional alkylating agent leading to DNA cross-links). Cells were reincubated for 15 to 40 days until surviving colonies exhibited greater than 30-50 cells. Plates were then stained with 1% methylene blue and the colonies counted, with surviving fraction determined relative to plating efficiency. Nine skin fibroblast cell strains from normal individuals were studied as controls. One neurofibromatosis (NF) cell strain, SB23, exhibited normal sensitivity to all three DNA-damaging agents studied in early (7-8) and middle (12-13) in vitro passage. Strain GM0622, on the other hand, exhibited normal sensitivity to the three DNA-damaging agents studied at early passage, but showed a significant decrease in survival after exposure to both gamma radiation (D0 = 106 rad) and actinomycin D (D0 = 0.024 mcg/ml) with increasing passage. Strain GM1639 exhibited decreased survival after actinomycin D exposure at early passage (D0 = 0.017 mcg/ml), with normal survival after exposure to gamma radiation and mitomycin C at the same passage. Cell strains exhibited decreasing low density plating efficiencies and growth rates with increasing passage such that study of cytotoxicity was not feasible after middle passage in strains SB23 and GM0622, and after early passage in strain GM1639. The results suggest that cultured fibroblast cell strains from patients with NF exhibit early in vitro senescence which sometimes is associated with an inability to handle certain DNA-damaging agents.

Preliminary report on ten patients with spinal cord injuries treated with hyperbaric oxygen

A preliminary report is presented on 10 patients with spinal cord injuries who were treated with hyperbaric oxygen. The results suggest that by supporting injured spinal cord tissue with oxygen under pressure, improvement in nerve function may occur. No deterioration of motor power or sensation was evident during or after hyperbaric oxygen treatment in any of these patients. The possible contribution of ischaemia to the pathology of spinal cord injury should encourage further experimental research and clinical trials with hyperbaric oxygen.

Central and peripheral object distances as determinants of the effective visual field in early infancy

While visually fixating on a central, coloured object, thirty-six infants aged between two and five months were presented with a peripheral target to the right or to the left of midline. Both objects were presented at two distances: either 30 or 90 cm from the infant. The extent of the effective visual field was measured by the presence and the latency of saccadic shifts of gaze from the fixation object toward the target object placed at varying degrees of eccentricity. The effective visual field expanded between two and four months. Near peripheral targets were detected at greater angles of eccentricity than those more distant, but this effect was modified both by age and by the distance of central fixation. For two- and three-month infants the effective visual field was most reduced when the central fixation object was placed at 30 cm and the target object at 90 cm. The ability to respond to peripheral objects more distant than the fixation object develops after three months.

A study of the effects of hyperbaric oxygen on the experimental spinal cord injury

The degree of motor recovery in sheep with a controlled contusion to the thoracic spinal cord is compared with the recovery in sheep treated with hyperbaric oxygen and confirms the results of a preliminary series previously reported. The degree of central cord cystic necrosis and degeneration in the surrounding white matter is compared in the control and treated animals. The improvement in motor recovery and in the degree of cord degeneration after treatment with hyperbaric oxygen suggests that ischaemia plays a significant role in the experimental animal with a contusion injury to the spinal cord.

Central necrosis following contusion to the sheep's spinal cord

This paper presents the results of a study on the pathological changes associated with post traumatic central spinal cord necrosis.

Treatment of paraplegic sheep with hyperbaric oxygen

The results of the use of hyperbaric oxygen therapy to control the onset of paraplegia after recent spinal cord injury in sheep are described. This preliminary report suggest that hyperbaric oxygen therapy instituted within two hours of the injury will result in improved motor recovery.

Sinus barotrauma in divers

Sinus barotrauma is a common occupational disease of divers, with the incidence of descent barotrauma approximately double that of ascent. Pain chronologically associated with the change of pressure is the most dominant symptom and is seen in 92% of the cases presented for treatment. The majority complain of a frontal distribution of pain, with ethmoidal and maxillary being much less significant. Epistaxis is the second commonest symptom, and may be the sole symptom in some ascent cases. A history of recent or past sinus barotrauma or upper respiratory tract pathology is very common. Clinical examination supports the evidence of upper respiratory tract pathology in many cases. The radiological signs of abnormality were present in over three quarters of the cases examined. Of these the maxillary sinus was affected in most cases, the frontal in approximately one quarter and the ethmoidal in less than a fifth. The pathology was more commonly that of mucosal thickening, but in 12% of cases there was a fluid level. It is noted that although symptoms were predominantly frontal, x-ray changes were most often present in the maxillary sinuses.