Mesenchymal stromal cells with chimaeric antigen receptors for enhanced immunosuppression

Allogeneic mesenchymal stromal cells (MSCs) are a safe treatment option for many disorders of the immune system. However, clinical trials using MSCs have shown inconsistent therapeutic efficacy, mostly owing to MSCs providing insufficient immunosuppression in target tissues. Here we show that antigen-specific immunosuppression can be enhanced by genetically modifying MSCs with chimaeric antigen receptors (CARs), as we show for E-cadherin-targeted CAR-MSCs for the treatment of graft-versus-host disease in mice. CAR-MSCs led to superior T-cell suppression and localization to E-cadherin+ colonic cells, ameliorating the animals' symptoms and survival rates. On antigen-specific stimulation, CAR-MSCs upregulated the expression of immunosuppressive genes and receptors for T-cell inhibition as well as the production of immunosuppressive cytokines while maintaining their stem cell phenotype and safety profile in the animal models. CAR-MSCs may represent a widely applicable therapeutic technology for enhancing immunosuppression.

AXL Inhibition Improves the Antitumor Activity of Chimeric Antigen Receptor T Cells

The receptor tyrosine kinase AXL is a member of the TYRO3, AXL, and proto-oncogene tyrosine-protein kinase MER family and plays pleiotropic roles in cancer progression. AXL is expressed in immunosuppressive cells, which contributes to decreased efficacy of immunotherapy. Therefore, we hypothesized that AXL inhibition could serve as a strategy to overcome resistance to chimeric antigen receptor T (CAR T)-cell therapy. To test this, we determined the impact of AXL inhibition on CD19-targeted CAR T (CART19)-cell functions. Our results demonstrate that T cells and CAR T cells express high levels of AXL. Specifically, higher levels of AXL on activated Th2 CAR T cells and M2-polarized macrophages were observed. AXL inhibition with small molecules or via genetic disruption in T cells demonstrated selective inhibition of Th2 CAR T cells, reduction of Th2 cytokines, reversal of CAR T-cell inhibition, and promotion of CAR T-cell effector functions. AXL inhibition is a novel strategy to enhance CAR T-cell functions through two independent, but complementary, mechanisms: targeting Th2 cells and reversing myeloid-induced CAR T-cell inhibition through selective targeting of M2-polarized macrophages.

Scientific echosounder data provide a predator's view of Antarctic krill (Euphausia superba)

Raw acoustic data were collected in East Antarctica from the RSV Aurora Australis during two surveys: the Krill Availability, Community Trophodynamics and AMISOR Surveys (KACTAS) and the Krill Acoustics and Oceanography Survey (KAOS) in the East Antarctic (centre coordinate 66.5° S, 63° E). The KACTAS survey was conducted between 14th to 21st January and 2001, and the KAOS survey was conducted between 16 January and 1 February 2003. We examine the Antarctic krill (Euphausia superba) component of these surveys and provide scientific echosounder (EK500 and EK60) data collected at 38, 120 and 200 kHz, cold water (-1 °C) echosounder calibration parameters and accompanying krill length frequency distributions obtained from trawl data. We processed the acoustic data to apply calibration values and remove noise. The processed data were used to isolate echoes arising from swarms of krill and to estimate metrics for each krill swarm, including internal density and individual swarm biomass. The krill swarm data provide insights to a predators' views of krill distribution and density.

Abstract 5074: Addition of MAPK inhibitors to prime and sensitize poorly differentiated thyroid cancers as a strategy to improve TSHR-CART cell therapy antitumor activity

Thyroid cancer is the most common endocrine cancer in the US, and its incidence is rising. Most thyroid cancer deaths are attributed to treatment-refractory, metastatic tumors. Thyroid stimulating hormone receptor (TSRH) expression is largely limited to the thyroid gland and is abundantly expressed on thyroid tumor cells, making TSRH a compelling target for advanced thyroid cancer diagnostics and therapeutics. Therefore, we developed a novel TSHR-targeted chimeric antigen receptor (CAR) T cell therapy to treat aggressive thyroid cancers. TSHR-CAR constructs were cloned into a lentiviral CAR construct containing 4-1BB and CD3ζ. First, we demonstrated potent TSHR-CART antigen-specific anti-tumor activity in vitro. Then, NOD-SCID-γ-/- (NSG) mice were inoculated subcutaneously with TSHR+ tumor cells and randomized by tumor volume to treatment with TSHR-CART cells or control Untransduced T cells (UTD). Treatment with TSHR-CART cells resulted in dose-dependent antitumor activity and prolonged survival. De-differentiated anaplastic thyroid cancers (ATC) downregulate TSHR. Our TSHR immunohistochemistry results corroborated these findings and displayed minimal TSHR protein expression, precluding successful TSHR-CART treatment. We therefore sought to sensitize these tumors with MAPK inhibitors, as a strategy to upregulate TSHR expression in patients with metastatic thyroid cancer. TSHR expression was upregulated in patient-derived xenograft (PDX) ATC models after one week of daily administration of the MAPK inhibitors (p=0.0024). After confirming that MAPK inhibition does not dampen TSHR-CART effector functions, we tested sequential and combination therapy of TSHR-CART with MEK and BRAF inhibition in vivo. NSG mice were engrafted with ATC BRAF-mutant PDX tumors and randomized by tumor volume to daily oral treatment with placebo or trametinib (MEK inhibitor) plus dabrafenib (BRAF inhibitor). One week later, mice received either UTD or TSHR-CART. Mice conditioned with trametinib plus dabrafenib (p=0.0018) and subsequently treated with TSHR-CART showed superior antitumor activity. However, the improved antitumor activity in this setting was transient. We therefore tested the durability of TSHR upregulation following MEK/BRAF inhibition and demonstrated that TSHR upregulation lasts less than 48-72 hours after discontinuation. Finally, we tested the combination of TSHR CART cells with MEK/BRAF inhibitors in ATC BRAF-mutant PDX tumors. Here, combining TSHR-CART cells with MEK/BRAF inhibitors result in durable control of the tumors. Collectively, our findings indicate that MEK/BRAF inhibition of de-differentiated thyroid cancers upregulated TSHR expression and enhanced TSHR-CART antitumor activity. This work represents a viable strategy to improve outcomes of patients with aggressive, metastatic thyroid cancers.

Citation Format: Claudia Manriquez Roman, Kendall J. Schick, Justyna J. Gleba, Truc N. Huynh, Elizabeth L. Siegler, James L. Miller, Aylin Alasonyalilar Demirer, Matthew L. Pawlush, Ahmet Biligili, Long K. Mai, Erin Tapper, Leo R. Sakemura, Michelle J. Cox, Carli M. Stewart, Ismail Can, Ekene J. Ogbodo, Gaofeng Cui, Georges Mer, Gloria R. Olivier, Yushi Qiu, Robert C. Smallridge, Zubair C. Abba, Han W. Tun, John A. Copland, Saad S. Kenderian. Addition of MAPK inhibitors to prime and sensitize poorly differentiated thyroid cancers as a strategy to improve TSHR-CART cell therapy antitumor activity. [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 5074.

Abstract 4082: Impact of immunosuppressive monocytes on CART19 cell effector functions and outcomes

CD19 directed chimeric antigen receptor T (CART19) cell therapy has resulted in remarkable outcomes in B cell malignancies and was FDA approved in multiple indications. However, durable remissions are limited to 40% of treated patients. Inhibitory myeloid cells in tumor microenvironment have been found to suppress T cell expansion and contribute to failure of CART19 cell therapy. In this study, we aimed to unravel the interactions between monocytes, CART19 cells and tumor cells to understand how monocytes-CART19 cell interactions impact CART19 cell effector functions and clinical outcomes. Two sets of experiments were conducted, 1) use of healthy CART19 cells, CD19+ tumor cells, and healthy monocytes; 2) use of brexu-cel products from ZUMA-2 clinical trial treating mantle cell lymphoma (MCL), patient-matched monocytes and circulating MCL tumor cells (n = 11; 6 durable responders, 2 relapsed after initial response and 3 non-responders).

CD28 costimulated CART19 (CART19-28ζ) cells generated in the lab from healthy donors were co-cultured with donor freshly isolated monocytes in the presence of Jeko-1 cells (a CD19+ MCL cell line). CART19 antigen specific proliferation was not inhibited by freshly isolated monocytes. When monocytes were co-cultured with CART19 and tumor cells, higher levels of eotaxin, GRO, MCP-3 and IL-7 were detected. When CART19 cells were co-cultured with the CD19+ JeKo-1 cells in the presence of ex vivo M2 polarized macrophages, CART19 antigen specific proliferation was inhibited (p=0.0045). Transwell experiments demonstrate that M2-induced CART19 inhibition is not contact dependent. Cytokine profile analysis indicated increased level of IL-1ra, IP-10 and MCP-1 and decreased level of IL-17A, sCD40L, IL-9 and MIP-1α when M2 macrophages were co-cultured with CART19 and tumor cells compared to co-cultures of tumor cells and CART19.

Then we conducted ex vivo co-cultures of brexu-cel products, autologous monocytes and circulating MCL tumor cells from MCL patients (ZUMA-2) collected prior to CART19 cell infusion. Here we observed trends of elevation of IL-13 and IL-5 and reduction of GRO, MCP-3, MIP-1β and IL-8 in non-responders, compared to responders (durable responses or relapsed patients).

Our results support that monocyte- and macrophage-dependent cytokine release could modulate CART19 effector and trafficking functions, and thus CART19 clinical outcomes. This warrants further investigation around strategies to improve durable responses to CART cell therapy.

Citation Format: Kun Yun, Reona Leo Sakemura, Michelle J. Cox, Truc Huynh, Claudia Manriquez-Roman, Olivia Sirpilla, Carli M. Stewart, James H. Girsch, Ekene J. Ogbodo, Ismail Can, Brooke Kimball, Lionel A. Kankeu Fonkoua, Mehrdad Hefazi, Michael W. Ruff, Elizabeth L. Siegler, Mike Mattie, Sao-Mai Nguyen-Mau, Simone Filosto, Saad S. Kenderian. Impact of immunosuppressive monocytes on CART19 cell effector functions and outcomes. [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 4082.

Abstract 1153: IL-4 depletion leads to the improvement of CART cell therapy

While chimeric antigen receptor T-cell therapy targeting CD19 (CART19) has shown remarkable success in the treatment of hematological malignancies, the durable response rates remain approximately 40% and there are limited solutions for CART cell therapy in the treatment of solid tumors. To further understand mechanisms of resistance, including CART cell exhaustion, we employed three independent approaches: 1) RNA and ATAC sequencing on unstimulated vs. exhausted healthy donor CART19 cells by utilizing an in vitro model for exhaustion, 2) RNA and ATAC sequencing on pre-infusion CART19 cell products from responders and non-responders in the Zuma-1 clinical trial that led to the FDA approval of axi-cel CART19 therapy, and 3) a genome-wide CRISPR knockout screen in healthy donor CART19 cells using our in vitro model for exhaustion.

In each of these approaches, IL-4 was identified as a regulator of CART cell dysfunction. In approach 1, ingenuity pathway analysis of genes that were both differentially accessible and expressed in exhausted compared with unstimulated CART19 cells revealed IL-4 as a top upstream regulator (p = 5E-6). In approach 2, IL-4 was one of two genes that were both upregulated and more accessible in CART19 cell products from non-responders (p < 5E-2). Finally, in approach 3, gene ontology enrichment analysis of genes that were positively selected during the genome-wide CRISPR knockout screen, revealed regulation of the IL-4 pathway as one of the top affected pathways (p = 1E-4).

Together, our data indicates a role for IL-4 in CART cell dysfunction caused by exhaustion. Investigating this mechanism further, we saw an increase in the production of IL-4 as CART cells became exhausted (p = 4E-3). Treatment of CART19 cells with human recombinant IL-4 (hrIL-4) resulted in dysfunction as evident by a decrease in antigen specific cytotoxicity (p = 4E-3) and proliferative ability (p= 6.5E-2), as well as exhaustion-specific signs of dysfunction such as an increase in the expression of the inhibitory receptor, TIM-3 (p = 3E-3) and an increase in the transcription of the exhaustion-related transcription factor EOMES (p = 1E-2).

Finally, we tested whether IL-4 neutralization enhances CART19 cell functions. Using a CD19+ JeKo-1 xenograft mouse model, we compared the combination treatment of CART19 cells and an IL-4 neutralizing monoclonal antibody (10 mg/Kg, clone # MP4-25D2) to CART19 cells and an IgG control. IL-4 neutralization in combination with CART19 cells resulted in reduced tumor burden (p = 4.6E-2), increased CART cell proliferation (p = 8E-3), and prolonged overall survival (p= 5E-2). In summary, our data indicates that 1) IL-4 induces CART cell dysfunction through a state of exhaustion and 2) IL-4 neutralization with a monoclonal antibody enhances CART cell therapy. As such, this novel combination therapy holds the potential to be translated to the clinic to improve durable responses from CART cell therapy.

Citation Format: Carli Stewart, Michelle J. Cox, Reona Sakemura, Ekene J. Ogbodo, Ismail Can, Claudia Manriquez Roman, Kun Yun, Olivia Sirpilla, James H. Girsch, Truc Huynh, Elizabeth L. Siegler, Jenny J. Kim, Mike Mattie, Nathalie Scholler, Simone Filosto, Saad S. Kenderian. IL-4 depletion leads to the improvement of CART cell therapy [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 1153.

Targeting cancer-associated fibroblasts in the bone marrow prevents resistance to CART-cell therapy in multiple myeloma

Pivotal clinical trials of B-cell maturation antigen-targeted chimeric antigen receptor T (CART)-cell therapy in patients with relapsed/refractory multiple myeloma (MM) resulted in remarkable initial responses, which led to a recent US Food and Drug Administration approval. Despite the success of this therapy, durable remissions continue to be low, and the predominant mechanism of resistance is loss of CART cells and inhibition by the tumor microenvironment (TME). MM is characterized by an immunosuppressive TME with an abundance of cancer-associated fibroblasts (CAFs). Using MM models, we studied the impact of CAFs on CART-cell efficacy and developed strategies to overcome CART-cell inhibition. We showed that CAFs inhibit CART-cell antitumor activity and promote MM progression. CAFs express molecules such as fibroblast activation protein and signaling lymphocyte activation molecule family-7, which are attractive immunotherapy targets. To overcome CAF-induced CART-cell inhibition, CART cells were generated targeting both MM cells and CAFs. This dual-targeting CART-cell strategy significantly improved the effector functions of CART cells. We show for the first time that dual targeting of both malignant plasma cells and the CAFs within the TME is a novel strategy to overcome resistance to CART-cell therapy in MM.

Challenges of CAR T-cell Therapy in CLL: Lessons Learned

Development of chimeric antigen receptor T (CART) cell therapy has led to unprecedented success against B cell leukemia and lymphoma and resulted in FDA-approved treatment protocols. Despite the initial clinical response in B cell-related malignancies, high relapse rates suggest that much work is needed to uncover mechanisms of resistance. In chronic lymphocytic leukemia (CLL), the durable activity of CAR T-cells is limited, and CART cell success is lower than in other malignancies. T cells from these patients are vulnerable to a state of dysfunction due to stresses including chronic infection, rapid cell cycle upon antigen recognition, immunosuppressive tumor microenvironment, and cancer-related treatments. T cells are also introduced to additional stresses when cultured ex vivo during the CART manufacturing process. All these factors contribute to the limited regenerative capacity of T cells, which can lead to CART treatment failure. In this short report, we will review the challenges of CAR T-cell therapy in patients with CLL and discuss potential strategies to overcome these challenges.

Development of a Clinically Relevant Reporter for Chimeric Antigen Receptor T-cell Expansion, Trafficking, and Toxicity

Although chimeric antigen receptor T (CART)-cell therapy has been successful in treating certain hematologic malignancies, wider adoption of CART-cell therapy is limited because of minimal activity in solid tumors and development of life-threatening toxicities, including cytokine release syndrome (CRS). There is a lack of a robust, clinically relevant imaging platform to monitor in vivo expansion and trafficking to tumor sites. To address this, we utilized the sodium iodide symporter (NIS) as a platform to image and track CART cells. We engineered CD19-directed and B-cell maturation antigen (BCMA)-directed CART cells to express NIS (NIS⁺CART19 and NIS⁺BCMA-CART, respectively) and tested the sensitivity of ¹⁸F-TFB-PET to detect trafficking and expansion in systemic and localized tumor models and in a CART-cell toxicity model. NIS⁺CART19 and NIS⁺BCMA-CART cells were generated through dual transduction with two vectors and demonstrated exclusive ¹²⁵I uptake in vitro. ¹⁸F-TFB-PET detected NIS⁺CART cells in vivo to a sensitivity level of 40,000 cells. ¹⁸F-TFB-PET confirmed NIS⁺BCMA-CART-cell trafficking to the tumor sites in localized and systemic tumor models. In a xenograft model for CART-cell toxicity, ¹⁸F-TFB-PET revealed significant systemic uptake, correlating with CART-cell in vivo expansion, cytokine production, and development of CRS-associated clinical symptoms. NIS provides a sensitive, clinically applicable platform for CART-cell imaging with PET scan. ¹⁸F-TFB-PET detected CART-cell trafficking to tumor sites and in vivo expansion, correlating with the development of clinical and laboratory markers of CRS. These studies demonstrate a noninvasive, clinically relevant method to assess CART-cell functions in vivo.

Leukemic extracellular vesicles induce chimeric antigen receptor T cell dysfunction in chronic lymphocytic leukemia

Chimeric antigen receptor (CAR) T cell therapy has yielded unprecedented outcomes in some patients with hematological malignancies; however, inhibition by the tumor microenvironment has prevented the broader success of CART cell therapy. We used chronic lymphocytic leukemia (CLL) as a model to investigate the interactions between the tumor microenvironment and CART cells. CLL is characterized by an immunosuppressive microenvironment, an abundance of systemic extracellular vesicles (EVs), and a relatively lower durable response rate to CART cell therapy. In this study, we characterized plasma EVs from untreated CLL patients and identified their leukemic cell origin. CLL-derived EVs were able to induce a state of CART cell dysfunction characterized by phenotypical, functional, and transcriptional changes of exhaustion. We demonstrate that, specifically, PD-L1+ CLL-derived EVs induce CART cell exhaustion. In conclusion, we identify an important mechanism of CART cell exhaustion induced by EVs from CLL patients.

Resistance to CART cell therapy: lessons learned from the treatment of hematological malignancies

Chimeric antigen receptor T (CART) cell immunotherapy has yielded significant clinical success in treating certain hematological malignancies. However, despite high initial response rates, most patients eventually relapse. Resistance to CART cell therapy can stem from tumor cell mutations, T cell defects, and tumor microenvironment (TME) immunosuppression. Tumor cells can downregulate target antigen expression to evade CART cell detection or mutate death receptor pathways to resist CART cell cytotoxicity. Patient T cells can be intrinsically defective, and CART cells often undergo exhaustion. The TME is abundant with immunosuppressive cells and factors which contribute to suboptimal CART cell activity. Collectively, issues originating in tumor cells, T cells, and the TME present significant hurdles to long-term remission after CART cell therapy. Various strategies to combat CART cell resistance have shown promise in preclinical studies and early clinical trials and are crucial to achieving durable responses.

The characteristics of krill swarms in relation to aggregating Antarctic blue whales

We model the presence of rare Antarctic blue whales (Balaenoptera musculus intermedia) in relation to the swarm characteristics of their main prey species, Antarctic krill (Euphausia superba). A combination of visual observations and recent advances in passive acoustic technology were used to locate Antarctic blue whales, whilst simultaneously using active underwater acoustics to characterise the distribution, size, depth, composition and density of krill swarms. Krill swarm characteristics and blue whale presence were examined at a range of spatiotemporal scales to investigate sub meso-scale (i.e., <100 km) foraging behaviour. Results suggest that at all scales, Antarctic blue whales are more likely to be detected within the vicinity of krill swarms with a higher density of krill, those found shallower in the water column, and those of greater vertical height. These findings support hypotheses that as lunge-feeders of extreme size, Antarctic blue whales target shallow, dense krill swarms to maximise their energy intake. As both Antarctic krill and blue whales play a key role in the Southern Ocean ecosystem, the nature of their predator-prey dynamics is an important consideration, not only for the recovery of this endangered species in a changing environment, but for the future management of Antarctic krill fisheries.

Using CRISPR/Cas9 to Knock Out GM-CSF in CAR-T Cells

Chimeric antigen receptor T (CAR-T) cell therapy is a cutting edge and potentially revolutionary new treatment option for cancer. However, there are significant limitations to its widespread use in the treatment of cancer. These limitations include the development of unique toxicities such as cytokine release syndrome (CRS) and neurotoxicity (NT) and limited expansion, effector functions, and anti-tumor activity in solid tumors. One strategy to enhance CAR-T efficacy and/or control toxicities of CAR-T cells is to edit the genome of the CAR-T cells themselves during CAR-T cell manufacturing. Here, we describe the use of CRISPR/Cas9 gene editing in CAR-T cells via transduction with a lentiviral construct containing a guide RNA to granulocyte macrophage colony-stimulating factor (GM-CSF) and Cas9. As an example, we describe CRISPR/Cas9 mediated knockout of GM-CSF. We have shown that these GM-CSF^k/o CAR-T cells effectively produce less GM-CSF while maintaining critical T cell function and result in enhanced anti-tumor activity in vivo compared to wild type CAR-T cells.

Factor V Leiden and Thermolabile Methylenetetrahydrofolate Reductase in Extreme Old Age

Both factor V Leiden and the C677T methylenetetrahydrofolate reductase (MTHFR) gene mutation are associated with premature vascular disease, and yet are found at surprisingly high allele frequencies in European populations, 2.7% and 35% respectively. We have investigated the prevalence of these mutations in 87 UK residents over the age of ninety, to look for any evidence of their association with premature death.

Five factor V Leiden heterozygotes were found, giving an allele frequency of 2.9%, similar to that in the general UK population. The frequency of the thermolabile C677T MTHFR mutation was 36% with 11% homozygotes, again similar to that in the UK population; these genotypes are in Hardy-Weinberg equilibrium, suggesting that there is not strong selection against the homozygous state. One person was both heterozygous for factor V Leiden and homozygous for the C677T mutation. This study suggests that neither factor V Leiden nor thermolabile MTHFR are risk factors for premature death.

Levels of agreement between student and staff assessments of clinical skills in performing cavity preparation in artificial teeth

OBJECTIVE

To determine the level of agreement between staff and students' assessment of clinical skills in performing tasks related to cavity preparation on a traditional dental manikin.

METHODS

Two studies were conducted with two successive student cohorts: Study 1-138 year 1 BDS students in a 2009/10 cohort and Study 2-135 students in a 2010/11 cohort. Staff members and students rated the students' performance in preparing a cavity on a traditional dental manikin using artificial teeth: hand-held (Study 1) and located in a lower jaw (Study 2). A 5-item criterion-related scoring rubric was developed. The rubric assessed students' abilities to hold the instrument correctly, determine the angle of entry to the tooth, remove the caries, conserve healthy tissues and avoid pulp exposure.

RESULTS

Agreement between the students' self-assessment and the staff's assessment was high for three of the five criteria (i.e. removal of artificial caries on the cavity wall, removal of artificial caries from the cavity floor and avoidance of pulp exposure). Levels of agreement for the remaining two criteria were moderate. A change in task difficulty affected the levels of agreement between staff and students, such that the more difficult the task, the greater the discrepancy in ratings.

CONCLUSIONS

Students tend to overrate the quality of their performance when compared with staff ratings. Task difficulty has an impact on levels of agreement.

Parallel proton transfer pathways in aqueous acid-base reactions

We study the mechanism of proton transfer (PT) between the photoacid 8-hydroxy-1,3, 6-pyrenetrisulfonic acid (HPTS) and the base chloroacetate in aqueous solution. We investigate both proton and deuteron transfer reactions in solutions with base concentrations ranging from 0.25 M to 4 M. Using femtosecond midinfrared spectroscopy, we probe the vibrational responses of HPTS, its conjugate photobase, the hydrated proton/deuteron, and chloroacetate. The measurement of these four resonances allows us to follow the sequence of proton departure from the acid, its uptake by the water solvent, and its arrival at the base. In recent studies it was shown that proton transfer to carboxylate bases proceeds via Grotthuss conduction through a water wire connecting the acid and the base [Mohammed et al., Science 310, 83 (2005);Agnew. Chem. Int. Ed. 46, 1458 (2007);Siwick and Bakker, J. Am. Chem. Soc. 129, 13412 (2007); J. Phys. Chem. B 112, 378 (2008)]. Here we show that, for the weaker base chloroacetate, an alternative channel for proton transfer arises. In this channel the proton is first transferred to the water solvent and only later taken up from the water by the base. We study the base concentration dependence of the two competing channels.

Medication safety program reduces adverse drug events in a community hospital

BACKGROUND

There is widespread interest in improving medication safety, particularly in the hospital setting. Numerous suggestions have been made as to how this should be done, but there is a paucity of data demonstrating the effectiveness of any of the interventions that have been proposed.

OBJECTIVES

To assess the impact of a wide ranging, community hospital based patient safety program on patient harm as measured by the rate of adverse drug events.

DESIGN

An audit of discharged hospital patients was conducted from January 2001 to December 2003. Baseline data were collected for the first 6 months and multiple drug protocols and other interventions were instituted on the nursing units and in the pharmacy department over the subsequent 9 months (transition period). These interventions were largely based on information about medication risks acquired from internal medication event reporting. Each month of the study adverse drug events (ADE) were sought from a random sample of inpatient charts. A trigger tool was used to detect clues to ADEs, the presence of which was confirmed or excluded by detailed manual chart review. The severity of these events was categorized using the classification system of the National Coordinating Council for Medication Error and Reporting and Prevention.

MAIN OUTCOME MEASURES AND RESULTS

Median ADEs per 1000 doses of medication dispensed declined significantly from 2.04 to 0.65 (p<0.001). Median ADEs per 100 patient days declined significantly from 5.07 to 1.30 (p<0.001). The proportion of inpatients with one or more ADE in the baseline period was 31% and declined threefold (p<0.001). The severity of reported medication events also declined. The number of ADEs associated conclusively with patient harm was 1.67 per total doses delivered in the baseline period and declined eightfold (p<0.001).

CONCLUSION

The implementation of a carefully planned series of low cost interventions focused on high risk medications, driven by information largely from internal event reporting, and designed to improve a hospital's medication safety leads to a significant decrease in patient harm.

Age-specific seroprevalence to an immunodominant Cryptosporidium sporozoite antigen in a Brazilian population

The seroepidemiology of Cryptosporidium infection was investigated in a representative sample of a normal population in the State of Sao Paulo, Brazil using a recombinant form of the immunodominant 27-kDa sporozoite antigen. IgG seropositivity was low in infants following loss of maternal antibody but quickly increased to approximately 60% by 5 years, then 80% by the age of 10 years, after which prevalence remained constant. The broad range of antibody concentrations is consistent with previous reports that the IgG response to C. parvum is short-lived. There is also evidence that average antibody concentrations increase with age. Results suggest that the recombinant antigen may be a more sensitive method of measuring seroprevalence than the native antigen in Western blot. Although cross-sectional studies can provide an insight into the epidemiology of C. parvum in normal populations, further studies investigating the dynamics of the humoral immune responses to Cryptosporidium and the use of serology in epidemiological studies are required.

Serological survey of anti-group A rotavirus IgM in UK adults

Rotaviral associated disease of infants in the UK is seasonal and infection in adults not uncommon but the relationship between these has been little explored. Adult sera collected monthly for one year from routine hospital samples were screened for the presence of anti-group A rotavirus immunoglobulin M class antibodies as a marker of recent infection. Anti-rotavirus IgM was seen in all age groups throughout the year with little obvious seasonal variation in the distribution of antibody levels. IgM concentrations and the proportion seropositive above a threshold both increased with age with high concentrations consistently observed in the elderly. Results suggest either high infection rates of rotavirus in adults, irrespective of seasonal disease incidence in infants, IgM persistence or IgM cross-reactivity. These results support recent evidence of differences between infant and adult rotavirus epidemiology and highlight the need for more extensive surveys to investigate age and time related infection and transmission of rotavirus.

Fathers' participation in family research: is there a self-selection bias?

The representativeness of fathers who participate in family research was examined among 661 families. Approximately two thirds of eligible fathers participated. Mothers' and observers' reports on families of participating and non-participating fathers were compared. Participating fathers underrepresented fathers with less education, later-born children, more ambivalent marriages, partners with more traditional child-rearing beliefs, families with less optimal parenting environments, and infants who were unplanned, had more difficult temperaments, and were less healthy. Also underrepresented were ethnic minority families and working-class fathers. However, no differences were found in regard to child gender, family income, mothers' psychosocial functioning, either parent's employment experiences, or child-care arrangements. Implications for the generalizability of findings and the recruitment of fathers are discussed.

Nosocomial primary bloodstream infections in intensive care unit patients in a nonteaching community medical center: a 21-month prospective study

All patients admitted to the medical and surgical intensive care units of a 500-bed nonteaching suburban hospital were followed prospectively for the occurrence of nosocomial primary bloodstream infections for 21 months. The incidence of primary bloodstream infection was 38 (1%) of 3163 patients; among patients with central venous catheters, it was 34 (4%) of 920 patients, or 4.0 infections per 1000 catheter-days. Ventilator-associated pneumonia, congestive heart failure, and each intravascular catheter inserted were independently associated with the development of a nosocomial primary bloodstream infection. Among infected patients, the crude mortality rate was 53%, and these patients had longer stays in intensive care units and the hospital than did uninfected patients. Bloodstream infection, however, was not an independent risk factor for death. The incidence, risk factors, and serious outcomes of bloodstream infections in a nonteaching community hospital were similar to those seen in tertiary-care teaching hospitals.

Venomous snake husbandry in Thailand

A captive breeding program for venomous Thai snakes was established at the Queen Saovabha Memorial Institute at Bangkok, Thailand. This was necessary to secure a stable, healthy, and species-confirmed source of snake venom for antivenom production. In 1994, wild-caught specimens were collected, sexed, quarantined, and housed appropriately. All data in this report, with the exclusion of Table 6, were collected from 1994 to 1997. Two species were bred successfully in captivity to date during this study period. Although captive breeding has not yet been achieved with all species and subspecies, our early success was encouraging.

Isolation and phenotypic characterization of Pseudomonas aeruginosa pseudorevertants containing suppressors of the catabolite repression control-defective crc-10 allele

The amiE gene encodes an aliphatic amidase capable of converting fluoroacetamide to the toxic compound fluoroacetate and is one of many genes whose expression is subject to catabolite repression control in Pseudomonas aeruginosa. The protein product of the crc gene, Crc, is required for repression of amiE and most other genes subject to catabolite repression control in this bacterium. When grown in a carbon source such as succinate, wild-type P. aeruginosa is insensitive to fluoroacetamide (due to repression of amiE expression). In contrast, mutants harboring the crc-10 null allele cannot grow in the presence of fluoroacetamide (due to lack of repression of amiE). Selection for succinate-dependent, fluoroacetamide-resistant derivatives of the crc-10 mutant yielded three independent pseudorevertants containing suppressors that restored a degree of catabolite repression control. Synthesis of Crc protein was not reestablished in these pseudorevertants. All three suppressors of crc-10 were extragenic, and all three also suppressed a Delta crc::tetA allele. In each of the three pseudorevertants, catabolite repression control of amidase expression was restored. Catabolite repression control of mannitol dehydrogenase production was also restored in two of the three isolates. None of the suppressors restored repression of glucose-6-phosphate dehydrogenase or pyocyanin production.

The spherical aberration of the crystalline lens of the human eye

The in vivo spherical aberration of the lenses of 26 subjects was estimated from the measured total aberration of the eye and that predicted from the measured shape of the anterior corneal surface. Since it was only possible to estimate the aberration contribution from the posterior corneal surface, its value led to an uncertainty in the final aberration level of the lens. For all the subjects and for a wide range of possible aberration levels at the posterior corneal surface, the spherical aberration of the relaxed lens was found to be negative.

Failure of glove hole detection device for synthetic gloves

Holes in latex gloves can be reliably detected by commercially available electronic devices. The purpose of this study was to compare the performance of an electronic glove hole detection device using latex gloves to that of neoprene, vinyl, and nitrile latex-free gloves. The electronic hole detection device accurately detected holes in the latex gloves during the 2-h study. In contrast, the latex-free gloves were immediately conductive of electricity in the absence of holes. Consequently, electronic glove hole detection devices cannot be reliably used with latex-free gloves.

Malaria transmission and naturally acquired immunity to PfEMP-1

Why there are so few gametocytes (the transmission stage of malaria) in the blood of humans infected with Plasmodium spp. is intriguing. This may be due either to reproductive restraint by the parasite or to unidentified gametocyte-specific immune-mediated clearance mechanisms. We propose another mechanism, a cross-stage immunity to Plasmodium falciparum erythrocyte membrane protein 1 (PfEMP-1). This molecule is expressed on the surface of the erythrocyte infected with either trophozoite or early gametocyte parasites. Immunoglobulin G antibodies to PfEMP-1, expressed on both life cycle stages, were measured in residents from an area where malaria is endemic, Papua New Guinea. Anti-PfEMP-1 prevalence increased with age, mirroring the decline in both the prevalence and the density of asexual and transmission stages in erythrocytes. These data led us to propose that immunity to PfEMP-1 may influence malaria transmission by regulation of the production of gametocytes. This regulation may be achieved in two ways: (i) by controlling asexual proliferation and density and (ii) by affecting gametocyte maturation.

Modeling the impact of subclinical measles transmission in vaccinated populations with waning immunity

An increasing body of evidence suggests that a substantial proportion of individuals who respond to measles vaccine display an antibody boost accompanied by mild or no symptoms on exposure to wild virus. It is unknown whether this emerging class of individuals can support transmission. The epidemiologic consequences of vaccinated individuals able to transmit virus are investigated using a mathematical model. Parameters for this model are estimated using regression analysis on a Canadian serologic data set. The authors confirm that neutralizing antibodies are decaying significantly in absence of circulating virus. Based on a protective threshold plaque reduction neutralization (PRN) titer of 120, the authors estimate the mean duration of vaccine-induced protection in absence of reexposure to be 25 years (95% confidence interval (CI) 18, 48). After long-term absence of circulating virus, the mathematical model predicts that 80% (95% CI 65, 91) of all seroconverted vaccinees have titers below the protective threshold. In this case, elimination of measles virus cannot be achieved by a single-dose routine vaccination strategy if the basic reproduction number in vaccinated individuals exceeds 1.24 (95% CI 1.10, 1.53). For this reason, there is a need to establish the intensity and duration of infectiousness in vaccinated individuals.

Effect of aging on the monochromatic aberrations of the human eye

We measured the contrast sensitivity (CS) of a group of older subjects through natural pupils and compared the results with those from a group of younger subjects. We also measured each subject's monochromatic ocular wave-front aberrations using a crossed-cylinder aberroscope and calculated their modulation transfer functions (MTF's) and root-mean-squared (RMS) wave-front aberrations for fixed pupil diameters of 4 mm and 6 mm and for a natural pupil diameter. The CS at a natural pupil diameter and the MTF computed for a fixed pupil diameter were found to be significantly poorer for the older group than for the younger group. However, the older group showed very similar MTF's and significantly smaller RMS wave-front aberrations compared with the younger group at their natural pupil diameters, owing to the effects of age-related miosis. These results suggest that although monochromatic ocular wave-front aberrations for a given pupil size increase with age, the reduction in CS with age is not due to this increase.

The effect of surround luminance on measurements of contrast sensitivity

We investigated how the luminance of an immediate surround to a visual target affects the measurement of contrast sensitivity. We examined four young, healthy, subjects under typical lighting conditions for each test but varied the surround luminance systematically by controlling a backlit surround. The effect of varying the surround on contrast sensitivity measurements made with a Pelli-Robson chart was minimal. The only statistically significant difference was between measurements made with a 900 cd.m-2 surround compared to those made with 5.6, 9, or 30 cd.m-2 surrounds when tested at a viewing distance of 4 m. The higher luminance surround produced higher levels of contrast sensitivity. The effect of the surround luminance was greater when measuring contrast sensitivity to sinewave gratings using a method of constant stimuli. Optimum performance was found using a surround luminance of 9 cd.m-2 (20% of the mean target luminance). Statistically, a wide range of surround luminances (3-30 cd.m-2, or 7-67% mean target luminance) gave similar levels of visual performance, but higher luminance surrounds led to reduced contrast sensitivity. Possible reasons for the difference in the effect of the surround depending upon the test are discussed. Ophthalmic practitioners using contrast sensitivity measurements with letter charts probably need not make special efforts to illuminate the test surround appropriately. However, practitioners using sinewave gratings, especially computer generated sinewave gratings, to measure contrast sensitivity, may have their measurements affected by inappropriately lit task surrounds.

New advances in electronic devices for hole detection

Holes in surgical gloves are considered to be an important source of transmission of pathogens between surgeon and patient. Two new glove hole detectors have been devised to alert the surgeon to the presence of holes. These devices have been evaluated using six powder-free and seven powdered varieties of surgical gloves that were either dry or exposed to hydration. Eight of the 13 surgical gloves hydrated rapidly with water, altering their resistance to the conduction of electricity. Because the Barrier Integrity Monitor¿ only has a hydration monitor, 68 false positives occurred during the evaluation, indicating to the surgeon that he/she should change gloves unnecessarily because the glove had no hole. In contrast, the Surgic Alert Monitor¿ (SAM¿) had a hydration alarm as well as a glove hole detection alarm. During the 104 tests, the SAM¿ device showed no false positives. In the testing of five of the rapidly hydrating types of surgical gloves, the SAM¿ device could not reliably detect holes. On the basis of this study, the SAM¿ device, in conjunction with gloves that resist hydration, appeared to be a reliable hole detection monitor.

Infection with group C rotavirus in a suburban community in Brazil

Group C rotaviruses are associated with sporadic outbreaks of gastroenteritis worldwide. Age-specific seroprevalence of group C rotavirus antibodies was investigated in sera, randomly collected and representative of a suburban community in Brazil which had previously been screened for group A rotavirus antibodies. Antibody prevalence to group C rotavirus was low in children under 5 years and increased slowly with age to 36% seropositivity in adults, reflecting continuous exposure to primary infection in all age groups. This suggests a higher incidence of infection than disease might predict. Adult antibody prevalence was similar to that in other geographical settings. No obvious patterns of infection with group A and group C rotavirus were found within individuals, which suggests independent transmission. However, further epidemiological studies are required to understand group C rotavirus dynamics and possible interactions with group A rotavirus transmission and immunity.

Cross immunity and vaccination against multiple microparasite strains

We explore the equilibrium properties of a series of compartmental, ODE models describing the interaction between different strains of pathogen. The interaction is conceptualized as acting through shared antigens: infection and recovery from one strain leaves the host with a primed immune response against subsequent strains. The models consider the effect of this priming on susceptibility (the ability to be infected) and transmission (the ability to infect) in an SIR model. In these models, the specific past history of infection is encapsulated in different susceptible compartments within the model. In a third, SIS, model, specific past history is not included, but strains have differential abilities to infect previously infected hosts. Equilibrium results include criteria for the coexistence of strains. For the SIR models, the region of coexistence defined by parameters shrinks as the effect of strains on each other (increased antigenic similarity) increases. For the SIS model, coexistence depends critically on the rate at which complete susceptibility is recovered following infection, and coexisting strains must have differential abilities to infect completely and partially susceptible hosts. Interestingly, this model provides analogies to commensalism (the first species gains from the presence of the second; the second neither gains nor loses from the interaction) and symbiosis (the presence of both species benefits the other). Additionally, we show that the maximum number of coexisting strains is two in this model. The effect of vaccination depends on the initial strain structure, the ability of vaccination to mount protection to both strains and the coverage. Vaccination may allow a previously excluded strain to coexist or exist alone, and may allow a previously rarer strain to become more common with the possibility of increasing incidence of disease. We discuss the dynamics of these models, compare model results to observed patterns and consider additional model structures. The importance of these results to specific multi-strain pathogens, in particular rotavirus, is considered.

"Scientific basis of wound closure techniques." Evaluation of a new training program

A formal training program in wound repair entitled "Scientific Basis of Wound Closure Techniques" has been developed and is accredited by the Dannemiller Memorial Educational Foundation. This course is now available at no cost to medical schools, residencies, and continuing education programs for graduate physicians. A manual with its complementing videotape allow the course participant to gain the necessary psychomotor skills to repair wounds. Evaluation of the course taken by third-year medical students and first-year residents demonstrates a high level of satisfaction. After instituting the course, there was a noticeable change in the types of barriers, instruments, and wound closure techniques practiced in our emergency department.

Seroepidemiological study of respiratory syncytial virus in São Paulo state, Brazil

Transmission of respiratory syncytial virus is thought to be highly seasonal based on reported clinical cases, although transmission resulting in mild disease in all age groups has been little studied. This has been investigated in a seroepidemiological survey using sera from São Paulo, Brazil. Seroprevalence was found to increase rapidly with age, reaching over 90% by three years of age. This is typical of viral infections, which produce life-long immunity following primary infection. One-hundred percent seropositivity was attained by five years of age and maintained throughout adulthood, whereas mean antibody titers continued to increase with age. The mean duration of maternal antibodies was estimated to be 3.3 months with antibody decay demonstrated in paired samples from infants. The results are discussed in relation to possible mechanisms generating such a profile.

Seroepidemiology of group A rotavirus in suburban São Paulo, Brazil

Age-specific patterns of rotavirus infection were investigated using a randomly selected and representative sample of sera from a suburban community of São Paulo, Brazil screened for class-specific antibodies to group A rotavirus. Age-serology of anti-rotavirus IgG showed primary infection predominant in young infants with a median age of around 18 months consistent with IgM serology suggesting highest rates of recent infection between ages 4 and 48 months. Anti-rotavirus serum IgA prevalence increased gradually with age. Paired samples from infants, collected 1 month apart, indicated high exposure rates with seroconversion occurring in several infants during the reported low transmission season. Between 5 and 10% of adults had elevated IgM levels indicative of recent infection and, potentially, of an important contribution adults may play to rotavirus transmission. Further understanding of the dynamics of rotavirus transmission within populations, at group and serotype level, would benefit the design and monitoring of future immunization programmes.

Venomous snakebite in Thailand. I: Medically important snakes

Thailand has an abundance of venomous snakes. Among the neurotoxic family Elapidae, there are three species of the genus Naja (cobras), three of the genus Bungarus (kraits), and the king cobra of the genus Ophiophagus. Other Elapidae snakes in Thailand include sea snakes and Asian coral snakes of the genus Calliophis. They have potent venoms but rarely bite humans. Tissue and hemotoxic snakes are represented by family Viperidae, subfamilies Viperinae and Crotalinae. They remain an occupational hazard for farmers and rubber tappers, causing serious morbidity but only rare deaths, since competent treatment is now widely available throughout Thailand. Purified equine antivenin is manufactured locally for the monocled and Siamese spitting cobras (Naja kaouthia and N. siamensis), king cobra (Ophiophagus hannah), banded krait (Bungarus fasciatus), most green pit vipers (Trimeresurus sp.), Malayan pit viper (Calloselasma rhodostoma), and the Siamese Russell's viper (Daboia russelli siamensis).

Venomous snakebite in Thailand. II: Clinical experience

We reviewed a total of 2,525 snakebite patients in Bangkok. Of these, 1,415 were bitten by venomous snakes, 91 by neurotoxic snakes of genus Naja or Bungarus and 1,324 by snakes of family Viperidae or Crotalidae. Seventy-one percent of bites were on the lower extremity. There were two fatal cobra bites; both patients were dead on arrival at the hospital. Bites from vipers caused morbidity but no deaths. Species-specific antivenins are effective in reversing respiratory failure from cobra bites and coagulopathies from bites by Viperidae and Crotalidae snakes. However, early respiratory and wound care will save lives even in the absence of specific cobra and krait antivenin. Care of a snakebite victim should consist of immobilization and bandaging of the bitten limb with elastic bandages during transport to the hospital, early surgical debridement of necrotic tissue, appropriate infusion of antivenin, aggressive respiratory support, management of shock and infection, and peritoneal dialysis or hemodialysis. Incision of bite wounds, suctioning, application of ice, and tourniquets are of no proven value and may be dangerous. All snakebite victims in southeast Asia should survive if they receive early competent care.

Measles antibody levels in a vaccinated population in Brazil

An epidemiological study of measles-specific immunoglobulin G antibody levels was conducted using a representative sample of a vaccinated suburban population in São Paulo State, Brazil. The study aimed to determine immunity status in relation to age and infection or vaccination experience. 549 age-structured samples of sera, collected in 1990, were screened and calibrated to the international reference serum, using measles nucleoprotein in an enzyme immunoassay. In the age group with direct experience of vaccination (9 months to 15 years), whether routine or campaign, over 90% had detectable antibody > or = 50 miu/mL. However, 14% of these had antibody concentrations between 50 and 100 miu/mL and 30% between 50 and 255 miu/mL. In those over 15 years of age, 94% had antibody levels > 255 miu/mL, assumed to be the result of past infection. The study suggested that, within highly vaccinated populations, a proportion of individuals had measles antibody levels which may be insufficient to protect against reinfection or clinical disease. The implications of these results, and similar findings elsewhere, in relation to the persistence of measles requires investigation; this has particular relevance in São Paulo following the recent measles outbreak.

A compassionate response toward providing. Nutrition and hydration in vulnerable populations

Ethical guidelines provide a valuable first step in thinking about a new model of caring--one that brings together an enhanced model of patient autonomy, a clearer understanding of the moral (as opposed to merely biologic) meaning of life and death, a consistent concern for human life, and a recovery of the gerontological nurse practitioner's role as advocate, counselor, educator, and healer of the human spirit. Instead of creating a slippery slope, the emerging consensus will place decisions to withhold or withdraw fluids and nutrition on even firmer ethical, legal, and moral ground. Even in cases involving severe and enduring illness, disability, and "helplessness," society's focus must be on life. By its very nature, every human life, without reference to its condition, has a value that no one rightfully can deny or measure. Recognition of that truth is the cornerstone on which American law is built. Society's acceptance of that fundamental principle explains why, from time immemorial, society through law has extended its protection to all, including, especially, its weakest and most vulnerable members (Brophy v. New England Sinai Hospital., Inc., 1986).

A new computerized control unit for small bone surgical instruments

The SmartDrive console represents an important advance in small bone surgery because it monitors and coordinates the operation of its handpieces. The SmartDrive console has the following unique features: 1) a handpiece recognition system; 2) an instrument speed display; 3) a handpiece display and monitoring system; 4) a torque instrument control system; 5) a temperature monitoring system; 6) and an irrigation system. Mechanical performance studies have been undertaken that have validated the accuracy of the monitoring systems of the consoles. The consoles provided reliable recordings of the rotational speeds of their hi-speed drills. The MicroAire console automatically shuts off its power as the temperature increased to 110 degrees F (43 degrees C). In contrast, the Stryker Command 2 console has a limited monitoring system that can not alter the operation of the handpieces.

Factor V Leiden and thermolabile methylenetetrahydrofolate reductase in extreme old age

Both factor V Leiden and the C677T methylenetetrahydrofolate reductase (MTHFR) gene mutation are associated with premature vascular disease, and yet are found at surprisingly high allele frequencies in European populations, 2.7% and 35% respectively. We have investigated the prevalence of these mutations in 87 UK residents over the age of ninety, to look for any evidence of their association with premature death. Five factor V Leiden heterozygotes were found, giving an allele frequency of 2.9%, similar to that in the general UK population. The frequency of the thermolabile C677T MTHFR mutation was 36% with 11% homozygotes, again similar to that in the UK population; these genotypes are in Hardy-Weinberg equilibrium, suggesting that there is not strong selection against the homozygous state. One person was both heterozygous for factor V Leiden and homozygous for the C677T mutation. This study suggests that neither factor V Leiden nor thermolabile MTHFR are risk factors for premature death.

Grating detection and orientation discrimination in amblyopia

PURPOSE

We examined whether the misperceptions associated with amblyopic visual perception can be revealed under natural viewing conditions by comparing the ability to detect the presence of a grating with the ability to identify the grating orientation.

METHODS

Grating detection and orientation discrimination performance (horizontal versus vertical) were determined, using stimuli that consisted of sinusoidal gratings of fixed contrast (75%) but with variable spatial frequency. A total of four amblyopic subjects (two strabismic and two non-strabismic) and four age-matched normals participated in the experiment.

RESULTS

Psychometric functions for grating detection and orientation identification were found to be closely matched in the normal subjects and in all four amblyopic subjects, indicating that orientation could be correctly identified at detection threshold.

CONCLUSIONS

The absence of orientation uncertainty in the psychophysical data for the amblyopic observers is not consistent with the several previous reports of spatial aliasing in the central field of amblyopes. Our results suggest that non veridical visual perception in central amblyopic vision can not be revealed under natural viewing conditions by comparing the ability to detect the presence of a grating with the ability to identify its orientation. Possible reasons for the failure of this technique to reveal spatial aliasing in amblyopes are discussed.

Making things move--the options for computer-based displays

Two methods for producing moving stimuli on computer-controlled displays are discussed. The first method, memory manipulation, can take several forms: moving a memory window over a fixed memory image (memory windowing); moving the memory associated with objects and background for such objects (memory movement); and changing all the memory within the image on every frame of the display (memory animation). Memory windowing and movement are suitable for low memory or low processing-capacity computer systems, but are limited in their range of temporal stimulus properties. Memory animation is the most flexible of all display techniques available but requires higher memory or processing capacity or both. The second method, palette-manipulation, is akin to being able to change the contents of a book simply by changing the page numbers in its index. Look-up-table splitting, look-up-table bit-splitting and look-up-table rotation are all suitable for low memory or low processing-capacity computing systems. Look-up-table splitting allows independent control of the motion of one or several objects but severely limits the spatio-temporal properties of those objects. Look-up-table bit-splitting gives much more flexible control of the spatio-temporal properties of the stimulus but is useful only for very brief stimulus presentations. Look-up-table rotation provides good control of stimulus temporal properties but limits the spatial properties of the stimuli. Look-up-table animation provides excellent spatial and temporal control of periodic stimuli but, unless stimuli are presented in spatio-temporal quadrature, requires high memory or processing capacity or both.