Baseline serum levels of IgA anti-cyclic citrullinated protein antibodies in early rheumatoid arthritis predict radiographic progression after 11 years of treatment: a secondary analysis of the CIMESTRA study

OBJECTIVE

Smoking and periodontitis are risk factors for developing rheumatoid arthritis (RA), suggesting a break of tolerance on mucosal surfaces. Immunoglobulin A (IgA) antibodies are part of the mucosal immune system. The dominant autoantibodies in RA are anti-cyclic citrullinated protein antibodies (ACPAs), and IgG and IgA subclasses exist simultaneously. This study aimed to investigate the association of ACPA IgA subtypes with disease activity and long-term radiographic outcomes in RA, compared with ACPA IgG.

METHOD

Total ACPA IgG, IgA, IgA1, and IgA2 were quantified in serum from patients with early RA (n = 97). Patient characteristics, IgM rheumatoid factor (IgM-RF) status, clinical and biochemical disease activity scores, and radiographic status evaluated by total Sharp score (TSS), were assessed at baseline and after 2 and 11 years of treatment.

RESULTS

All patients with ACPA IgA also had ACPA IgG. ACPA IgA positivity was associated with IgM-RF and male gender. Both ACPA IgA and IgG levels at baseline were weakly associated with disease activity markers. Baseline ACPA IgA and IgG did not show a linear correlation with radiographic status after 10 years, but could predict radiographic progression (ΔTSS ≥ 5 from 0 to 11 years), with positive likelihood ratios of 3.7 and 4.0, respectively.

CONCLUSION

ACPA IgA and IgG were weakly associated with disease activity in early RA. RA patients with a ΔTSS ≥ 5 after 11 years of treatment had higher ACPA IgG and ACPA IgA levels at baseline; however, none of the ACPA subtypes was superior in predicting long-term radiographic progression.

Is the Pattern Changing? Atrial Fibrillation and Screening with Holter Electrocardiograms among Ischemic Stroke Patients in Greenland from 2016 to 2021

A standardized examination regime for ischemic stroke (IS) patients was implemented in Greenland in 2010. Prevalence of atrial fibrillation (AF) of 32% was found among discharged IS patients from 2011 to 2012, and our study aims to estimate the use of Holter ECGs for AF diagnostics and the current prevalence of AF among IS patients in Greenland. Patients discharged from Queen Ingrid's Hospital in Nuuk between 2016 and 2021 with an ICD-10 diagnosis of IS or stroke without specification were included. Data on Holter recordings, age, gender, medical treatment with rivaroxaban or warfarin, and ICD-10 and ICPC codes for AF were extracted for each patient. The overall incidence of IS from 2016 to 2021 was 133/100,000 and unchanged since 2012. Sixty-eight of the study's IS patients (14.5%) had AF, and 46% of IS patients with Holter data accessible had a recording according to international recommendations. Our results indicate that fewer IS patients in Greenland have AF than previously. However, the insufficient use of Holter as a diagnostic tool may explain part of the drop, as well as improved preventive treatment with rivaroxaban among AF patients in Greenland. Regardless, IS remains common, and a focus on diagnostics and preventable risk factors should be maintained.

Treatment Provided in Children and Adolescents with Functional Seizures-A Danish Nationwide Cohort

BACKGROUND

Functional seizures (FS) are episodes of paroxysmal involuntary movements and altered consciousness without the typical changes in the electroencephalography as with epilepsy. A multidisciplinary approach is the golden standard in the treatment of FS. This study examined the cross-sectoral collaboration and treatment modalities provided to children and adolescents after a diagnosis of FS.

METHOD

A Danish nationwide cohort, consisting of 334 children and adolescents, aged 5-17 years, with a validated diagnosis of FS during the period 2004-2014 was studied. Medical record data were collected from diagnosing hospital departments. Management and treatment modalities from the time of diagnosis up to three months after diagnosis were explored.

RESULTS

The most used treatment modalities were psychoeducation (n = 289, 86.5%) and follow-up in outpatient care (n = 192, 70.6%). A cross-sectoral collaboration was initiated for a third of cases (n = 98, 29.3%). The most commonly provided treatment combination consisted of psychoeducation, follow-up in outpatient care and psychotherapy; however, only a few patients received this specific combination (n = 14, 4.2%).

CONCLUSIONS

The treatment applied was individualized and consisted of varying use of treatment modalities. Initiatives to curate clinical guidelines and implement a multidisciplinary treatment approach should be further explored to improve treatment for this young group of patients.

Lithium induced hypercalcemia: an expert opinion and management algorithm

BACKGROUND

Lithium is the gold standard prophylactic treatment for bipolar disorder. Most clinical practice guidelines recommend regular calcium assessments as part of monitoring lithium treatment, but easy-to-implement specific management strategies in the event of abnormal calcium levels are lacking.

METHODS

Based on a narrative review of the effects of lithium on calcium and parathyroid hormone (PTH) homeostasis and its clinical implications, experts developed a step-by-step algorithm to guide the initial management of emergent hypercalcemia during lithium treatment.

RESULTS

In the event of albumin-corrected plasma calcium levels above the upper limit, PTH and calcium levels should be measured after two weeks. Measurement of PTH and calcium levels should preferably be repeated after one month in case of normal or high PTH level, and after one week in case of low PTH level, independently of calcium levels. Calcium levels above 2.8 mmol/l may require a more acute approach. If PTH and calcium levels are normalized, repeated measurements are suggested after six months. In case of persistent PTH and calcium abnormalities, referral to an endocrinologist is suggested since further examination may be needed.

CONCLUSIONS

Standardized consensus driven management may diminish the potential risk of clinicians avoiding the use of lithium because of uncertainties about managing side-effects and consequently hindering some patients from receiving an optimal treatment.

Experiences, perspectives, and practice patterns of pulmonary embolism follow-up in Denmark. A mixed method study informing the development of A sTrucTurEd INtegrateD post PE care model

Background

Practice patterns of follow-up after pulmonary embolism (PE) varies both within and between countries, and high-quality evidence to provide clinical guidance is lacking [1,2]. This study is part of the trial – A sTrucTurEd INtegrateD post Pulmonary Embolism care model (Attend-PE) aimed at developing and testing the effectiveness of a structured, integrated and patient-centered follow-up care model for patients with PE.

Purpose

To explore experiences, perspectives, and practice patterns of PE follow-up. Ultimately identifying and describing the opportunity space for a structured integrated post PE care model.

Methods

We performed a convergent mixed method study based on data from patient journey mapping including surveys, observations, and semi-structured patient interviews across all main hospitals treating PE in Denmark. An integrated mixed methods interpretation was conducted using joint displays.

Results

Main results are presented in joint displays in Figure 1 and 2. Observations and surveys were conducted at 18 hospitals including 12 in-depth patient-interviews.

The structure of care varied greatly. Patients expressed a need for early follow up and specialist care but at 18% of the sites first follow-up visit was not until 3–6 months after PE and 24% of the sites only had in-person contact with patients when follow-up echocardiography was needed. At some sites it was also highlighted that not all patients were referred to the post PE follow-up. anticoagulation clinics. Further, transition of care to the general practitioner was identified as a particular challenge.

All sites considered Non-vitamin K antagonist oral anticoagulants the preferred anticoagulant treatment with low-molecular-weight heparins/Vitamin K antagonists as second choice. The possible need for extended treatment and reduced dose favored Rivaroxaban and Apixaban. The decision on treatment duration was most often taken at the 3–6-month follow-up visit, and patients described the decision on extended treatment as positive and reassuring.

Patient information (oral and written) varied greatly and was most often focused on anticoagulant treatment, while knowledge on PE in general, symptom management, and activity was scarce. Two sites offered structured group-based patient education, but unstructured patient education at the individual follow-up visits was most common.

Help and guidance on managing post-PE symptoms and returning to everyday life was perceived essential by patients, as it affected them both physically and mentally. However, none of the sites routinely offered or referred patients to rehabilitation.

Involvement of relatives was considered important but 33% of the hospital sites did not systematically encourage relatives to attend follow-up.

Conclusion

The considerable variation in structure of PE follow-up care demonstrated in this mixed method study highlights the need for a structured integrated post pulmonary embolism care model.

Funding Acknowledgement

Type of funding sources: Private grant(s) and/or Sponsorship. Main funding source(s): The Danish Heart AssociationThe Novo Nordisk Foundation

Psychiatric Disorders in Children and Adolescents With Psychogenic Nonepileptic Seizures

OBJECTIVE

Knowledge regarding psychiatric disorders in children and adolescents with psychogenic nonepileptic seizures (PNES) is limited. This study outlines the spectrum and risk of psychiatric disorders in childhood-onset PNES.

METHODS

We performed a nationwide matched cohort study of children and adolescents with PNES 5 to 17 years of age at the time of diagnosis between January 1, 1996, and December 31, 2014. Two matched comparison groups were included: children and adolescents with epilepsy (ES) and children and adolescents without PNES or epilepsy, called healthy controls (HC). Outcomes were prevalent psychiatric disorders before index (i.e., date of diagnosis or corresponding date for HC) and incident psychiatric disorders 2 years after index. Relative risks (RRs) were calculated and adjusted for potential confounders.

RESULTS

We included 384 children and adolescents with validated PNES, 1,152 with ES, and 1,920 HC. Among the cases of PNES, 153 (39.8%) had prevalent psychiatric disorders and 150 (39.1%) had incident psychiatric disorders. Compared to the ES and HC groups, children and adolescents with PNES had elevated risks of both prevalent psychiatric disorders (adjusted RR_PNES/ES 1.87, 95% confidence interval [CI] 1.59-2.21, adjusted RR_PNES/HC 5.54, 95% CI 4.50-6.81) and incident psychiatric disorders (adjusted RR_PNES/ES 2.33, 95% CI 1.92-2.83, adjusted RR_PNES/HC 8.37, 95% CI 6.31-11.11). A wide spectrum of specific psychiatric disorders displayed elevated RRs.

CONCLUSIONS

Children and adolescents with PNES are at higher risk of a wide range of psychiatric disorders compared to children and adolescents with ES and HC. A careful psychiatric evaluation is warranted to optimize and individualize treatment.

[Functional neurological symptoms and the positive diagnostic process]

Functional neurological symptoms are common in neurology and general medical practice. Functional neurological symptoms refer to neurological symptoms, which are not explained by a defined disease. The most common are functional weakness and non-epileptic seizures. Psychiatric models have dominated the classification, aetiology and treatment, limiting the neurologist's role to making the diagnosis by excluding disease and pronouncing the symptoms to be psychogenic. In this review, we outline the possibility of a positive diagnostic process, which can be the first step of treatment.

Assessing peristomal skin changes in ostomy patients: validation of the Ostomy Skin Tool

BACKGROUND

Peristomal skin problems are common and are treated by a variety of health professionals. Clear and consistent communication among these professionals is therefore particularly important. The Ostomy Skin Tool (OST) is a new assessment instrument for the extent and severity of peristomal skin conditions. Formal tests of reliability and validity are necessary for its use in clinical practice, research, and education.

OBJECTIVES

To estimate inter- and intra nurse assessment variability of the OST and validity by comparison to a 'gold standard' (GS) defined by an expert panel.

METHODS

Thirty photographs of peristomal skin were presented twice to 20 ostomy care nurses--10 from Denmark (DK) and 10 from Spain (ES)--to determine intra- and inter nurse assessment variability. The same photographs were presented to an international group of experts (dermatologist and ostomy care nurses), to establish a GS for comparison and validation of the results.

RESULTS

A high intra-nurse assessment agreement, κ=0·84, was found with no differences in the intra-nurse assessments from the two groups of nurses (DK and ES). The inter-nurse assessment agreement was 'moderate to good', κ=0·54, with the agreement between the experts higher, κ=0·70. A high correlation between the scores from the nurses and the GS were seen in the lower part of the two scales [Discoloration, Erosion, Tissue overgrowth (DET) score<7)].

CONCLUSION

The study supported the validity of the OST. It is suggested that a categorical scale can be used to illustrate the severity of the DET scores.

Effect of red wine and red grape extract on blood lipids, haemostatic factors, and other risk factors for cardiovascular disease

OBJECTIVE

Some epidemiological studies found a lower risk of cardiovascular disease among wine drinkers than among drinkers of other types of ethanol. This difference might be due to an effect of nonalcohol compounds in wine on important cardiovascular risk factors. The objective of this study was to compare the effect of red wine, nonalcohol compounds of red wine and placebo on established cardiovascular risk factors.

DESIGN

A parallel, four-armed intervention study.

SUBJECTS

A total of 69 healthy 38-74-y-old men and women.

INTERVENTIONS

Subjects were randomised to either 1: red wine (males: 300 ml/day, 38.3 g alcohol/day, female subjects: 200 ml/day, 25.5 g alcohol/day), 2: water + red grape extract tablets (wine-equivalent dose), 3: water + red grape extract tablets (half dose), or 4: water + placebo tablets for a period of 4 weeks. No other sources of alcohol or anthocyanin were allowed. Plasma high-density lipoprotein (HDL)-cholesterol (HDL-C), low-density lipoprotein (LDL)-cholesterol (LDL-C), HDL-C/LDL-C-ratio, very-low-density lipoprotein (VLDL)-triacylglycerol, total cholesterol, fibrinogen, factor VII coagulant activity (FVIIc), blood pressure, and body weight were determined before and after intervention.

RESULTS

Wine consumption was associated with a significant 11-16% increase in fasting HDL-C and 8-15% decrease in fasting fibrinogen relative to not drinking wine. There were no significant treatment effects on fasting LDL-C, HDL-C/LDL-C-ratio, VLDL-triacylglycerol, total cholesterol, FVIIc, or blood pressure. Drinking wine was associated with relative body weight increments closely corresponding to the energy contributed by the alcohol component.

CONCLUSION

Moderate red wine consumption for 4 weeks is associated with desirable changes in HDL-C and fibrinogen compared with drinking water with or without red grape extract. The impact of wine on the measured cardiovascular risk factors thus seems primarily explained by an alcohol effect. Our finding suggests that the putative difference in cardiac risk associated with wine vs other alcoholic beverages might be rather explained by other life-style confounders than by red wine contents of nonalcohol components.

Effect of 8 week intake of probiotic milk products on risk factors for cardiovascular diseases

OBJECTIVE

To investigate the effect of a probiotic milk product containing the culture CAUSIDO(R) and of two alternative products on risk factors for cardiovascular disease in overweight and obese subjects.

DESIGN

An 8 week randomized, double-blind, placebo- and compliance-controlled, parallel study.

SUBJECTS

Seventy healthy, weight-stable, overweight and obese (25.0<BMI<37.5 kg/m2) males (n=20) and females (n=50), 18-55 y old, were randomly assigned into five groups.

INTERVENTION

Four groups consumed 450 ml fermented milk products (yoghurt) daily. Group 1: a yoghurt fermented with two strains of Streptococcus thermophilus and two strains of Lactobacillus acidophilus (StLa). Group 2: a placebo yoghurt fermented with delta-acid-lactone (PY). Group 3: a yoghurt fermented with two strains of Streptococcus thermophilus and one strain of Lactobacillus rhamnosus (StLr). Group 4: a yoghurt fermented with one strain of Enterococcus faecium and two strains of Streptococcus thermophilus (CAUSIDO(R) culture), GAIO(R) (G). The dietary composition of the yoghurt was otherwise similar. The fifth group was given two placebo pills (PP) daily.

RESULTS

When comparing all five treatment groups, unadjusted for changes in body weight, no statistical effects were observed in week 8 in the G-group on low density lipoproteins (LDL)-cholesterol (P=0.29). After adjustment for small changes in body weight, LDL-cholesterol decreased by 8.4% (0.26+/-0.10 mmol/l; P<0.05) and fibrinogen increased (0.74+/-0.32 mmol/l; P<0.05) after 8 weeks in the G-group. This was significantly different from the group consuming chemically fermented yoghurt and the group consuming placebo pills (P<0.05). After 8 weeks, systolic blood pressure was significantly more reduced in the StLa and G-group compared to StLr. No other differences were found.

CONCLUSION

The CAUSIDO(R) culture reduced LDL-cholesterol and increased fibrinogen in the overweight subjects at a 450 ml consumption daily for 8 weeks. The effect on LDL-cholesterol confirms previous studies. An immunostimulation by one of the strains in the product might explain the effect on fibrinogen in the G-group.

SPONSORSHIP

MD Foods A/S, Denmark.

A quantitative assay to measure the interaction between immunogenic peptides and purified class I major histocompatibility complex molecules

A direct and sensitive biochemical assay to measure the interaction in solution between peptides and affinity-purified major histocompatibility complex (MHC) class I molecules has been generated. Specific binding reflecting the known class I restriction of cytotoxic T cell responses was obtained. Adding an excess of beta 2-microglobulin (beta 2m) significantly increased the rate of peptide association, but it did not affect the rate of dissociation. Binding was complicated by a rapid and apparently irreversible loss of functional MHC class I at 37 degrees C which might limit the life span of empty MHC class I thereby preventing the inadvertent exchange of peptides at the target cell surface. All class I molecules tested bound peptides of the canonical octa- to nona-meric length. However, one class I molecule, Kk, also bound peptides, which were much longer suggesting that the preference of class I molecules for short epitopes is not absolute and may be caused by factors other than the peptide-MHC class I binding event itself.

The interaction between beta 2-microglobulin (beta 2m) and purified class-I major histocompatibility (MHC) antigen

The function of MHC class-I molecules is to sample peptides from the intracellular environment and present them to CD8+ cytotoxic T lymphocytes. To understand the molecular details of the assembly (and disassembly) of peptide-beta 2m-class-I complexes a biochemical peptide-class-I binding assay has been generated recently and this paper reports on a similar assay for the interaction between beta 2m and class I. As a model system human beta 2m binding to mouse class I was used. The assay is strictly biochemical using purified reagents which interact in solution and complex formation is determined by size separation. It is specific and highly sensitive. The observed affinity of the interaction, KD, is close to 0.4 nM. The rate of association at 37 degrees C is very fast (the ka is around 5 x 10(4)/M/s) whereas the dissociation is slow (the kd is around 8 x 10(-6)/s); the ratio of dissociation to association yields a calculated KD close to the observed value. At 37 degrees C almost all of the purified class I participates in binding of the exogenously offered beta 2m showing that a considerable exchange of the endogenous beta 2m occurs. Finally, it was demonstrated that exogenous beta 2m enhances binding to MHC class-I of short perfectly-matching peptides as well as longer peptides.

A mouse aminopeptidase N is a marker for antigen-presenting cells and appears to be co-expressed with major histocompatibility complex class II molecules

To analyze the expression of mouse aminopeptidase N (APN) on the cells of the immune system a panel of rat monoclonal antibodies against mouse intestinal APN was generated. These antibodies were used to affinity purify functional mouse APN from both intestine and kidney, and by flow cytometry to examine the APN expression of the cells of the mouse immune system. An APN closely related, perhaps identical, to the intestinal APN was expressed on a subpopulation of spleen cells and stimulated peritoneal exudate cells, primarily representing antigen-presenting cells, such as B cells, macrophages, dendritic cells, and veiled cells. In contrast this APN expression could not be detected on thymocytes or spleen T cells. As a corollary, APN was expressed on monocyte, macrophage, and B lymphoma cell lines, but not on T hybridoma or thymoma cell lines. The expression of APN showed a striking correlation with the MHC class II expression in all the cell populations studied. This apparent co-expression suggests a role for APN in antigen processing.

MHC molecules protect T cell epitopes against proteolytic destruction

There is a subtle duality in the role of proteolytic enzymes in Ag processing. They are required to fragment protein Ag ingested by APC. However, prolonged exposure to proteolytic enzymes may lead to a complete degradation of the Ag, leaving nothing for the T cell system to recognize. What ensures that some of the Ag is salvaged? Using a cell-free system we demonstrate that an Ag fragment, once bound to a MHC class II molecule, is effectively protected against proteolytic destruction by cathepsin B and pronase E. The bound fragment, however, can be modified by aminopeptidase N. We suggest that MHC class II molecules play an important regulatory role in the physiologic processing of Ag.

MHC molecules protect T cell epitopes against proteolytic destruction

There is a subtle duality in the role of proteolytic enzymes in Ag processing. They are required to fragment protein Ag ingested by APC. However, prolonged exposure to proteolytic enzymes may lead to a complete degradation of the Ag, leaving nothing for the T cell system to recognize. What ensures that some of the Ag is salvaged? Using a cell-free system we demonstrate that an Ag fragment, once bound to a MHC class II molecule, is effectively protected against proteolytic destruction by cathepsin B and pronase E. The bound fragment, however, can be modified by aminopeptidase N. We suggest that MHC class II molecules play an important regulatory role in the physiologic processing of Ag.

pH dependence of the interaction between immunogenic peptides and MHC class II molecules. Evidence for an acidic intracellular compartment being the organelle of interaction

The pH dependence of the interaction between immunogenic peptide and MHC class II was studied both in a direct biochemical binding assay and in a functional Ag presentation assay. The two approaches yielded similar results. All of the peptides tested bound optimally to their relevant MHC class II restriction element at around pH 4.5. Indeed, several of the peptides did not bind at neutral pH. These results demonstrate that Ag under physiologic conditions meet MHC class II in a quite acidic environment. The very acidic pH optimal for peptide-MHC class II interaction is only found intracellularly and most notably in the endosome-lysosome compartment in which Ag processing is thought to occur. Thus, Ag processing and interaction with MHC class II molecules can potentially happen in the very same compartment. This yet undefined acidic compartment would have to contain proteolytic enzymes and MHC class II molecules.

pH dependence of the interaction between immunogenic peptides and MHC class II molecules. Evidence for an acidic intracellular compartment being the organelle of interaction

The pH dependence of the interaction between immunogenic peptide and MHC class II was studied both in a direct biochemical binding assay and in a functional Ag presentation assay. The two approaches yielded similar results. All of the peptides tested bound optimally to their relevant MHC class II restriction element at around pH 4.5. Indeed, several of the peptides did not bind at neutral pH. These results demonstrate that Ag under physiologic conditions meet MHC class II in a quite acidic environment. The very acidic pH optimal for peptide-MHC class II interaction is only found intracellularly and most notably in the endosome-lysosome compartment in which Ag processing is thought to occur. Thus, Ag processing and interaction with MHC class II molecules can potentially happen in the very same compartment. This yet undefined acidic compartment would have to contain proteolytic enzymes and MHC class II molecules.

Efficacy of HLö-7 and pyrimidoxime as antidotes of nerve agent poisoning in mice

The toxicity and efficacy of two oximes, HLö-7 and pyrimidoxime, were evaluated in mice and compared to those obtained with HI-6. HLö-7 and pyrimidoxime produced 24 h LD50 values of 356 and 291 mg/kg (i.p.), respectively. In combination with atropine (17.4 mg/kg, i.p.), HLö-7 was a very efficient therapy against poisoning by 3 x LD50 dose of soman, sarin and GF and 2 x LD50 dose of tabun with ED50 values of 12.4, 0.31, 0.32 and 25.2 mg/kg, respectively. In contrast, pyrimidoxime was a relatively poor therapy which resulted in ED50 values of greater than 150, 5.88, 100 and 71 mg/kg against poisoning by soman, sarin, GF and tabun, respectively. HLö-7 produced significant (p less than 0.05) reactivation of phosphorylated acetylcholinesterase, in vivo, resulting in 47, 38, 27 and 10% reactivation of sarin, GF, soman and tabun inhibited mouse diaphragm acetylcholinesterase, respectively. HLö-7 also antagonized sarin-induced hypothermia in mice suggesting that it reactivated central acetylcholinesterase. The potential of HLö-7 as a replacement oxime for the treatment of nerve agent poisoning is discussed.

Comparison of several oximes against poisoning by soman, tabun and GF

Three oximes currently being evaluated for adoption as replacement nerve agent therapy by various countries were compared for therapeutic efficacy against the toxic organophosphate inhibitors soman and tabun under a standard set of conditions. These oximes together with PAM-Cl and toxogonin, were also compared for efficacy against GF, an agent weaponized by Iraq. The order of effectiveness against soman was HI-6 greater than HLö-7 greater than pyrimidoxime. HLö-7 was very effective against tabun poisoning while HI-6 and pyrimidoxime were of moderate value. Against GF, HI-6 and HLö-7 were extremely effective, toxogonin was moderately effective, and PAM-Cl and pyrimidoxime were the least effective. HI-6 provided a high level of protection against all of the agents tested as did HLö-7 to a slightly lesser degree. The other oximes suffered from their lack of effects against one or more of the organophosphates.

Toxicity of organophosphate nerve agents and related phosphonylated oximes compared to their anticholinesterase activity in neuron cultures

Oximes, such as pralidoxime and toxogonin, are important therapeutic agents for the treatment of organophosphate (OP) nerve agent poisoning. Oximes can react with these nerve agents to give intermediates, phosphonylated oximes, which may be equally toxic to the parent OP. The sc LD50s of a series of phosphonylated 2-butanone and 2,3-butanedione monoximes were compared to the sc LD50s of their parent OPs (tabun, sarin, and VX) in CD-1 mice. In every case the derivatives were significantly less toxic than their parent nerve agents. Times to death, and to signs of poisoning, were inversely proportional to the dose of test compound, and in all mortalities, blood serum acetylcholinesterase (AChE) was severely inhibited. The relative potencies of these compounds, as well as soman, cyclohexyl methylphosphonofluoridate, and diisopropyl fluorophosphate, as inhibitors of AChE in primary cultures of mouse embryo neurons, correlated with their in vivo toxicities. The results indicate that mouse embryo neuron cultures may be a useful model with which to study this class of compounds.