Incorporating reproductive system history data into cardiovascular nursing research to advance women's health

The lack of sex-specific variables, such as reproductive system history (RSH), in cardiovascular research studies is a missed opportunity to address the cardiovascular disease (CVD) burden, especially among women who face sex-specific risks of developing CVD. Collecting RSH data from women enrolled in research studies is an important step towards improving women's cardiovascular health. In this paper, we describe two approaches to collecting RSH in CVD research: extracting RSH from the medical record and participant self-report of RSH. We provide specific examples from our own research and address common data management and statistical analysis problems when dealing with RSH data in research.

Use of wearables for monitoring cardiometabolic health: A systematic review

INTRODUCTION

Cardiometabolic disorders (CMD) such as hyperglycemia, obesity, hypertension, and dyslipidemia are the leading causes of mortality and significant public health concerns worldwide. With the advances in wireless technology, wearables have become popular for health promotion, but its impact on cardiometabolic health is not well understood.

PURPOSE

A systematic literature review aimed to describe the features of wearables used for monitoring cardiometabolic health and identify the impact of using wearables on those cardiometabolic health indicators.

METHODS

A systematic search of PubMed, CINAHL, Academic Search Complete, and Science and Technology Collection databases was performed using keywords related to CMD risk indicators and wearables. The wearables were limited to sensors for blood pressure (BP), heart rate (HR), electrocardiogram (ECG), glucose, and cholesterol.

INCLUDED STUDIES

1) were published from 2016 to March 2021 in English, 2) focused on wearables external to the body, and 3) examined wearable use by individuals in daily life (not by health care providers). Protocol, technical, and non-empirical studies were excluded.

RESULTS

Out of 53 studies, the types of wearables used were smartwatches (45.3%), patches (34.0%), chest straps (22.6%), wristbands (13.2%), and others (9.4%). HR (58.5%), glucose (28.3%), and ECG (26.4%) were the predominant indicators. No studies tracked BP or cholesterol. Additional features of wearables included physical activity, respiration, sleep, diet, and symptom monitoring. Twenty-two studies primarily focused on the use of wearables and reported direct impacts on cardiometabolic indicators; seven studies used wearables as part of a multi-modality approach and presented outcomes affected by a primary intervention but measured through CMD-sensor wearables; and 24 validated the precision and usability of CMD-sensor wearables.

CONCLUSION

The impact of wearables on cardiometabolic indicators varied across the studies, indicating the need for further research. However, this body of literature highlights the potential of wearables to promote cardiometabolic health.

Sex differences in the impact of physical frailty on outcomes in heart failure

BACKGROUND

Physical frailty is strongly related to adverse outcomes in heart failure (HF), and women are more likely to be physically frail than men; however, it is unknown if this sex difference affects outcomes.

OBJECTIVES

To determine if there are sex differences in the associations between physical frailty and health-related quality of life (HRQOL) and clinical outcomes in HF.

METHODS

We conducted a prospective study of adults with HF. Physical frailty was assessed using the Frailty Phenotype Criteria. HRQOL was assessed using the Minnesota Living with HF Questionnaire. One-year clinical events (all-cause death or cardiovascular hospitalization or emergency department visit) were ascertained. We used generalized linear modeling to quantify associations between physical frailty and HRQOL, and Cox proportional hazards modeling to quantify associations between physical frailty and clinical events, adjusting for Seattle HF Model scores.

RESULTS

The sample (n = 115) was 63.5 ± 15.7 years old and 49% women. Physical frailty was associated with significantly worse total HRQOL among women (p = 0.005) but not men (p = 0.141). Physical frailty was associated with worse physical HRQOL among both women (p < 0.001) and men (p = 0.043). There was a 46% higher clinical event risk for every one-point increase in physical frailty score among men (p = 0.047) but not women (p = 0.361).

CONCLUSIONS

Physical frailty is associated with worse overall HRQOL among women and higher clinical event risk among men, indicating a need to better understand contributors to sex-specific health differences associated with physical frailty in HF.

Candidate biomarkers of physical frailty in heart failure: an exploratory cross-sectional study

AIMS

Physical frailty is highly prevalent and predictive of worse outcomes in heart failure (HF). Candidate biomarker analysis may help in understanding the mechanisms underlying physical frailty in HF. We aimed to identify candidate biomarkers associated with physical frailty in HF using a multimarker strategy of distinct pathophysiological processes.

METHODS AND RESULTS

We collected data and plasma samples from 113 adults with New York Heart Association Functional Class I-IV HF. Physical frailty was measured with the Frailty Phenotype Criteria. Plasma biomarkers included: N-terminal pro-B-type natriuretic peptide, norepinephrine, dihydroxyphenylglycol, soluble tumour necrosis factor alpha receptor-1, adiponectin, insulin, glucose, insulin-like growth factor-1 (IGF-1), and myostatin. Comparative statistics and multivariate linear regression were used to test group differences and associations. The average age was 63.5 ± 15.7 years, half were women (48%), and most had a non-ischaemic aetiology of HF (73%). Physical frailty was identified in 42% and associated with female sex, higher body mass index and percent body fat, more comorbidities, and HF with preserved ejection fraction. Adjusting for Seattle HF Model projected survival score, comorbidities, body composition, and sex, physical frailty was associated with significantly lower plasma adiponectin [β ± standard error (SE) -0.28 ± 0.14, P = 0.047], IGF-1 (β ± SE -0.21 ± 0.10, P = 0.032), and myostatin (β ± SE -0.22 ± 0.09, P = 0.011). In sex-stratified analyses, IGF-1 and myostatin were significantly associated with physical frailty in men but not women.

CONCLUSION

We identified biomarkers involved in adipose tissue and skeletal muscle development, maintenance, and function that were associated with physical frailty in HF.

Frequency and Predictors of Falls Among Adults With Heart Failure: A Prospective Study

OBJECTIVE

Adults with heart failure (HF) may be at high risk for falling due to age, comorbidities and frailty; however, few studies have examined falls in HF. The purpose of this study was to quantify the frequency and predictors of falls over 1 year among adults with HF.

METHODS

We conducted a prospective study of adults with New York Heart Association (NYHA) functional class I-IV HF. After baseline assessment of physical frailty and clinical characteristics, participants self-reported falls every 3 months during 1 year. Comparative statistics were used to identify baseline differences between those who fell vs those who did not. A stepwise negative binomial regression model was used to identify predictors of fall rate over 1 year.

RESULTS

The sample (n = 111) was 63.4 ± 15.7 years old, 48% were women, 28% had HF with preserved ejection fraction, and 41% were frail. Over 1 year, 43 (39%) of participants reported at least 1 fall and 28 (25%) of participants reported 2+ falls. Among those who fell, 29 (67%) reported injurious falls. Those who fell had significantly higher body mass indexes and were more likely to have NYHA class III/IV, type 2 diabetes and HF with preserved ejection fraction and to meet slowness and physical exhaustion criteria than those who did not fall. The fall rate was elevated among those with type 2 diabetes and those meeting the slowness and physical exhaustion criteria for physical frailty.

CONCLUSIONS

Nearly 40% of adults with HF experienced a fall within 1 year. Screening for comorbidities, slowness and exhaustion may help to identify those at risk for a fall.

Unclassified white matter disorders: A diagnostic journey requiring close collaboration between clinical and laboratory services

BACKGROUND

Next generation sequencing studies have revealed an ever-increasing number of causes for genetic disorders of central nervous system white matter. A substantial number of disorders are identifiable from their specific pattern of biochemical and/or imaging findings for which single gene testing may be indicated. Beyond this group, the causes of genetic white matter disorders are unclear and a broader approach to genomic testing is recommended.

AIM

This study aimed to identify the genetic causes for a group of individuals with unclassified white matter disorders with suspected genetic aetiology and highlight the investigations required when the initial testing is non-diagnostic.

METHODS

Twenty-six individuals from 22 families with unclassified white matter disorders underwent deep phenotyping and genome sequencing performed on trio, or larger, family groups. Functional studies and transcriptomics were used to resolve variants of uncertain significance with potential clinical relevance.

RESULTS

Causative or candidate variants were identified in 15/22 (68.2%) families. Six of the 15 implicated genes had been previously associated with white matter disease (COL4A1, NDUFV1, SLC17A5, TUBB4A, BOLA3, DARS2). Patients with variants in the latter two presented with an atypical phenotype. The other nine genes had not been specifically associated with white matter disease at the time of diagnosis and included genes associated with monogenic syndromes, developmental disorders, and developmental and epileptic encephalopathies (STAG2, LSS, FIG4, GLS, PMPCA, SPTBN1, AGO2, SCN2A, SCN8A). Consequently, only 46% of the diagnoses would have been made via a current leukodystrophy gene panel test.

DISCUSSION

These results confirm the importance of broad genomic testing for patients with white matter disorders. The high diagnostic yield reflects the integration of deep phenotyping, whole genome sequencing, trio analysis, functional studies, and transcriptomic analyses.

CONCLUSIONS

Genetic white matter disorders are genetically and phenotypically heterogeneous. Deep phenotyping together with a range of genomic technologies underpin the identification of causes of unclassified white matter disease. A molecular diagnosis is essential for prognostication, appropriate management, and accurate reproductive counseling.

Background and Design of the Biological and Physiological Mechanisms of Symptom Clusters in Heart Failure (BIOMES-HF) Study

BACKGROUND

Symptoms, which often cluster together, are a significant problem in heart failure (HF). There is considerable heterogeneity in symptom burden, particularly in the vulnerable transition period after a hospitalization for HF, and the biological underpinnings of symptom during transitions are unclear. The purpose of this paper is to describe the background and design of a study that addresses these knowledge gaps, entitled "Biological and Physiological Mechanisms of Symptom Clusters in Heart Failure" (BIOMES-HF).

STUDY DESIGN AND METHODS

BIOMES-HF is a prospective gender- and age-balanced longitudinal study of 240 adults during the 6-month transition period after a HF hospitalization. The aims are to: 1) identify clusters of change in physical symptoms, 2) quantify longitudinal associations between biomarkers and physical symptoms, and 3) quantify longitudinal associations between physical frailty and physical symptoms among adults with heart failure. We will measure multiple symptoms, biomarkers, and physical frailty at discharge and then at 1 week and 1, 3, and 6 months post-hospitalization. We will use growth mixture modeling and longitudinal mediation modeling to examine changes in symptoms, biomarkers, and physical frailty post-HF hospitalization and associations therein.

CONCLUSIONS

This innovative study will advance HF symptom science by utilizing a multi-biomarker panel and the physical frailty phenotype to capture the multifaceted nature of HF. Using advanced quantitative modeling, we will characterize heterogeneity and identify potential mechanisms of symptoms in HF. As a result, this research will pinpoint amenable targets for intervention to provide better, individualized treatment to improve symptom burden in HF.

BRIEF LAY SUMMARY

Adults with heart failure may have significant symptom burden. This study is designed to shed light on our understanding of the role of biological and physiological mechanisms in explaining heart failure symptoms, particularly groups of co-occurring symptoms, over time. We will explore how symptoms, biomarkers, and physical frailty changes after a heart failure hospitalization. The knowledge generated from this study will be used to guide the management and self-care for adults with heart failure.

Assessing Cardiometabolic Health Risk in Children Living With Grandparent Primary Caregivers: Interim Analysis

Minimal research has been conducted on the effect that grandparents as primary caregivers have on the cardiometabolic health of children who live with them, even though a number of studies have examined the influence of parent caregivers. As a first step towards filling that gap, we examined physiological and behavioral indicators of cardiometabolic health risk among children (aged 7 to 12 years) living with grandparent primary caregivers in Oregon and Washington. We measured body mass index and total cholesterol/glycohemoglobin (HbA1c), as well as physical activity/sleep and diet. In this preliminary analysis of our findings with 10 dyads (mean age 64.2 ± 4.0 years for grandparents; 9.3 ± 1.9 years for grandchildren), we report that on most of the indicators - obesity, physical activity, sleep, and diet - these children’s levels were comparable to national averages across all household types (not differentiated by type of family structure). However, 25% of the grandchildren (n=2) participating in our study had a total cholesterol level ≥ 200, compared to 7.4% of children from a nationally representative dataset. Similarly, 14% of the grandchildren (n=1) participating in our study had HbA1c ≥ 6.5%, compared to < 0.5% of children from a nationally representative dataset. Our findings suggest that these children may be at higher cardiometabolic health risk (e.g., hyperlipidemia). Further investigations with a larger sample and more examination of cardiometabolic risk profiles including lipids/blood glucose assessment are required to validate our preliminary findings.

Characterizing Sex Differences in Physical Frailty Phenotypes in Heart Failure

BACKGROUND

Although women with heart failure (HF) are potentially more likely to be physically frail compared with men with HF, the underlying contributors to this sex difference are poorly understood. The purpose of this study was to characterize sex differences in physical frailty phenotypes in HF.

METHODS

We prospectively enrolled adults with class I-IV HF. Physical frailty was measured with the frailty phenotype criteria. Symptoms of dyspnea, sleep-related impairment, pain interference, depression, and anxiety were assessed. Body composition was measured using dual-energy x-ray absorptiometry. Simple comparative statistics and stepwise regression modeling were used.

RESULTS

The average age of the sample (n=115) was 63.6±15.7 years, 49% were women, and 73% had nonischemic cause. Forty-three percent of the sample was physically frail. Women had a 4.6 times greater odds of being physically frail compared with men, adjusting for covariates (odds ratio=4.63 [95% CI, 1.81-11.84], P=0.001). Both physically frail men and women were characterized by more type 2 diabetes, higher comorbidity burden, and worse dyspnea symptoms. Physically frail women had significantly worse symptoms compared with non-physically frail women but no difference in body composition characteristics. Physically frail men had significantly lower appendicular muscle mass, higher percent fat, lower hemoglobin, and more depressive symptoms compared with non-physically frail men.

CONCLUSIONS

Women are significantly more likely to be physically frail compared with men in HF. Physical frailty in both women and men is characterized by comorbidities and worse symptoms; physical frailty in men is characterized by worse physiological characteristics.

Gender differences in the prevalence of frailty in heart failure: A systematic review and meta-analysis

OBJECTIVES

This study quantitatively synthesized literature to identify gender differences in the prevalence of frailty in heart failure (HF).

BACKGROUND

The intersection of frailty and HF continues to garner interest. Almost half of patients with HF are frail; however, gender differences in frailty in HF are poorly understood.

METHODS

We performed a literature search to identify studies that reported prevalence of frailty by gender in HF. Random-effects meta-analysis was used to quantify the relative and absolute risk of frailty in women compared with men with HF, overall, and by Physical and Multidimensional Frailty measures. Meta-regression was performed to examine the influence of study age and functional class on relative risk in HF.

RESULTS

Twenty-nine studies involving 8854 adults with HF were included. Overall in HF, women had a 26% higher relative risk of being frail compared with men (95% CI = 1.14-1.38, z = 4.69, p < 0.001, I2 = 76.5%). The overall absolute risk for women compared to men with HF being frail was 10% (95% CI = 0.06-0.15, z = 4.41, p < 0.001). The relative risk of frailty was slightly higher among studies that used Physical measures (relative risk = 1.27, p < 0.001) compared with studies that used Multidimensional measures (relative risk = 1.24, p = 0.024). There were no significant relationships between relative risk and either study age or functional class.

CONCLUSIONS

In HF, frailty affects women significantly more than men. Future work should focus on elucidating potential causes of gender differences in frailty in HF.

Exploring gender differences in trajectories of clinical markers and symptoms after left ventricular assist device implantation

AIMS

Despite well-known gender differences in heart failure, it is unknown if clinical markers and symptoms differ between women and men after left ventricular assist device (LVAD) implantation. Our aim was to examine gender differences in trajectories of clinical markers (echocardiographic markers and plasma biomarkers) and symptoms from pre- to post-LVAD implantation.

METHODS AND RESULTS

This was a secondary analysis of data collected from a study of patients from pre- to 1, 3, and 6 months post-LVAD implantation. Data were collected on left ventricular internal end-diastolic diameter (LVIDd) and ejection fraction (LVEF), plasma N-terminal pro-B-type natriuretic peptide (NT-proBNP), and soluble suppressor of tumorigenicity (sST2). Physical and depressive symptoms were measured using the Heart Failure Somatic Perception Scale and Patient Health Questionnaire-9, respectively. Latent growth curve modelling was used to compare trajectories between women and men. The average age of the sample (n = 98) was 53.3 ± 13.8 years, and most were male (80.6%) and had non-ischaemic aetiology (65.3%). Pre-implantation, women had significantly narrower LVIDd (P < 0.001) and worse physical symptoms (P = 0.041) compared with men. Between pre- and 6 months post-implantation, women had an increase in plasma sST2 followed by a decrease, whereas men had an overall decrease (slope: P = 0.014; quadratic: P = 0.011). Between 1 and 6 months post-implantation, women had a significantly greater increase in LVEF (P = 0.045) but lesser decline in plasmoa NT-proBNP compared with men (P = 0.025).

CONCLUSION

Trajectories of clinical markers differed somewhat between women and men, but trajectories of symptoms were similar, indicating some physiologic but not symptomatic gender differences in response to LVAD.

Ibrexafungerp: A novel oral glucan synthase inhibitor

Ibrexafungerp is a novel glucan synthase inhibitor currently undergoing phase II and phase III clinical trials. This compound has demonstrated in vitro activity against clinically important fungal pathogens including Candida spp. and Aspergillus spp. It is able to retain activity against many echinocandin-resistant strains of Candida due to differential avidity for the target site compared to echinocandins. In vivo animal models have demonstrated efficacy in murine models of invasive candidiasis, aspergillosis, and pneumocystis. Due to high bioavailability, it can be administered both orally and intravenously. A favorable drug interaction and tolerability profile is observed with this compound. This review summarizes existing data that have either been published or presented at international symposia.

Variants in ACTG2 underlie a substantial number of Australasian patients with primary chronic intestinal pseudo-obstruction

BACKGROUND

Primary chronic intestinal pseudo-obstruction (CIPO) is a rare, potentially life-threatening disorder characterized by severely impaired gastrointestinal motility. The objective of this study was to examine the contribution of ACTG2, LMOD1, MYH11, and MYLK mutations in an Australasian cohort of patients with a diagnosis of primary CIPO associated with visceral myopathy.

METHODS

Pediatric and adult patients with primary CIPO and suspected visceral myopathy were recruited from across Australia and New Zealand. Sanger sequencing of the genes encoding enteric gamma-actin (ACTG2) and smooth muscle leiomodin (LMOD1) was performed on DNA from patients, and their relatives, where available. MYH11 and MYLK were screened by next-generation sequencing.

KEY RESULTS

We identified heterozygous missense variants in ACTG2 in 7 of 17 families (~41%) diagnosed with CIPO and its associated conditions. We also identified a previously unpublished missense mutation (c.443C>T, p.Arg148Leu) in one family. One case presented with megacystis-microcolon-intestinal hypoperistalsis syndrome in utero with subsequent termination of pregnancy at 28 weeks' gestation. All of the substitutions identified occurred at arginine residues. No likely pathogenic variants in LMOD1, MYH11, or MYLK were identified within our cohort.

CONCLUSIONS AND INFERENCES

ACTG2 mutations represent a significant underlying cause of primary CIPO with visceral myopathy and associated phenotypes in Australasian patients. Thus, ACTG2 sequencing should be considered in cases presenting with hypoperistalsis phenotypes with suspected visceral myopathy. It is likely that variants in other genes encoding enteric smooth muscle contractile proteins will contribute further to the genetic heterogeneity of hypoperistalsis phenotypes.

Ryanodine receptor type 3 (RYR3) as a novel gene associated with a myopathy with nemaline bodies

BACKGROUND AND PURPOSE

Nemaline myopathy (NEM) has been associated with mutations in 12 genes to date. However, for some patients diagnosed with NEM, definitive mutations are not identified in the known genes, suggesting that there are other genes involved. This study describes compound heterozygosity for rare variants in ryanodine receptor type 3 (RYR3) gene in one such patient.

METHODS AND RESULTS

Clinical examination of the patient at 22 years of age revealed a long narrow face, high arched palate and bilateral facial weakness. She had proximal weakness in all four limbs, mild scapular winging but no scoliosis. Muscle biopsy revealed wide variation in fibre size with type 1 fibre predominance and atrophy. Abundant nemaline bodies were located in perinuclear and subsarcolemmal areas, and within the cytoplasm. No likely pathogenic mutations in known NEM genes were identified. Copy number variation in known NEM genes was excluded by NEM-targeted comparative genomic hybridization array. Next-generation sequencing revealed compound heterozygous missense variants in the RYR3 gene. RYR3 transcripts are expressed in human fetal and adult skeletal muscle as well as in human brain and cauda equina samples. Immunofluorescence of human skeletal muscle revealed a 'single-row' appearance of RYR3, interspersed between the 'double rows' of ryanodine receptor type 1 (RYR1) at each A-I junction.

CONCLUSION

The results suggest that variants in RYR3 may cause a recessive muscle disease with pathological features including nemaline bodies. We characterize the expression pattern of RYR3 in human skeletal muscle and brain, and the subcellular localization of RYR1 and RYR3 in human skeletal muscle.

Genetics of alcohol consumption in Drosophila melanogaster

Individual variation in alcohol consumption in human populations is determined by genetic, environmental, social and cultural factors. In contrast to humans, genetic contributions to complex behavioral phenotypes can be readily dissected in Drosophila, where both the genetic background and environment can be controlled and behaviors quantified through simple high-throughput assays. Here, we measured voluntary consumption of ethanol in ∼3000 individuals of each sex from an advanced intercross population derived from 37 lines of the Drosophila melanogaster Genetic Reference Panel. Extreme quantitative trait loci mapping identified 385 differentially segregating allelic variants located in or near 291 genes at P < 10^-8 . The effects of single nucleotide polymorphisms associated with voluntary ethanol consumption are sex-specific, as found for other alcohol-related phenotypes. To assess causality, we used RNA interference knockdown or P{MiET1} mutants and their corresponding controls and functionally validated 86% of candidate genes in at least one sex. We constructed a genetic network comprised of 23 genes along with a separate trio and a pair of connected genes. Gene ontology analyses showed enrichment of developmental genes, including development of the nervous system. Furthermore, a network of human orthologs showed enrichment for signal transduction processes, protein metabolism and developmental processes, including nervous system development. Our results show that the genetic architecture that underlies variation in voluntary ethanol consumption is sexually dimorphic and partially overlaps with genetic factors that control variation in feeding behavior and alcohol sensitivity. This integrative genetic architecture is rooted in evolutionarily conserved features that can be extrapolated to human genetic interaction networks.

Experimental validation of a novel compact focusing scheme for future energy-frontier linear lepton colliders

A novel scheme for the focusing of high-energy leptons in future linear colliders was proposed in 2001 [P. Raimondi and A. Seryi, Phys. Rev. Lett. 86, 3779 (2001)]. This scheme has many advantageous properties over previously studied focusing schemes, including being significantly shorter for a given energy and having a significantly better energy bandwidth. Experimental results from the ATF2 accelerator at KEK are presented that validate the operating principle of such a scheme by demonstrating the demagnification of a 1.3 GeV electron beam down to below 65 nm in height using an energy-scaled version of the compact focusing optics designed for the ILC collider.

Mutations in RYR1 are a common cause of exertional myalgia and rhabdomyolysis

Mutations in the skeletal muscle ryanodine receptor (RYR1) gene are a common cause of neuromuscular disease, ranging from various congenital myopathies to the malignant hyperthermia (MH) susceptibility trait without associated weakness. We sequenced RYR1 in 39 unrelated families with rhabdomyolysis and/or exertional myalgia, frequent presentations in the neuromuscular clinic that often remain unexplained despite extensive investigations. We identified 9 heterozygous RYR1 mutations/variants in 14 families, 5 of them (p.Lys1393Arg; p.Gly2434Arg; p.Thr4288_Ala4290dup; p.Ala4295Val; and p.Arg4737Gln) previously associated with MH. Index cases presented from 3 to 45 years with rhabdomyolysis, with or without exertional myalgia (n=12), or isolated exertional myalgia (n=2). Rhabdomyolysis was commonly triggered by exercise and heat and, less frequently, viral infections, alcohol and drugs. Most cases were normally strong and had no personal MH history. Inconsistent additional features included heat intolerance, and cold-induced muscle stiffness. Muscle biopsies showed mainly subtle changes. Familial RYR1 mutations were confirmed in relatives with similar or no symptoms. These findings suggest that RYR1 mutations may account for a substantial proportion of patients presenting with unexplained rhabdomyolysis and/or exertional myalgia. Associated clinico-pathological features may be subtle and require a high degree of suspicion. Additional family studies are paramount in order to identify potentially MH susceptible relatives.

A novel explosive process is required for the γ-ray burst GRB 060614

Over the past decade, our physical understanding of gamma-ray bursts (GRBs) has progressed rapidly, thanks to the discovery and observation of their long-lived afterglow emission. Long-duration (> 2 s) GRBs are associated with the explosive deaths of massive stars ('collapsars', ref. 1), which produce accompanying supernovae; the short-duration (< or = 2 s) GRBs have a different origin, which has been argued to be the merger of two compact objects. Here we report optical observations of GRB 060614 (duration approximately 100 s, ref. 10) that rule out the presence of an associated supernova. This would seem to require a new explosive process: either a massive collapsar that powers a GRB without any associated supernova, or a new type of 'engine', as long-lived as the collapsar but without a massive star. We also show that the properties of the host galaxy (redshift z = 0.125) distinguish it from other long-duration GRB hosts and suggest that an entirely new type of GRB progenitor may be required.

In vivo evaluation of the effects of gravitational force (+Gz) on over-the-wire stainless steel Greenfield inferior vena cava filter in swine

This study was done to determine the effect of exposure to gravitational force (acceleration stress) on in vivo over-the-wire stainless steel Greenfield inferior vena cava filters. Fifteen pigs underwent venous cut down and placement of a stainless steel Greenfield filter. A 4-week observation period simulated realistic convalescence and allowed sufficient time for epithelialization. Ten pigs were exposed to acceleration stress in a centrifuge (3G run for 15 sec followed by rest until return to baseline heart rate, then a 9G run for 15 sec), with inertial loading in a head-to-tail direction (+Gz). Fluoroscopy during acceleration stress allowed assessment for filter migration. Five pigs were not exposed to acceleration stress. AP and lateral abdominal radiographs were obtained at post-filter placement, convalescence, and centrifuge exposure to determine the position and integrity of the filter. All 15 IVCs were resected and evaluated for gross or histological injury to the vessel wall. IVC filter placement was technically successful in all 15 pigs. Radiographic measurements were limited secondary to differences in pig positioning. Fluoroscopy showed no filter migration. All filters were securely attached to the vena cava by the hooks without gross evidence of perforation or hemorrhage. There were varying degrees of fibroplasia involving the hooks and tip of the filters in both the control and experimental groups. Histologically, there was evidence of prior hemorrhage at the level of the hooks, which was similar between the control and experimental groups. It is concluded that Greenfield filter position and vena caval integrity at the implantation site is unaffected by high acceleration stress.

Principal mutation hotspot for central core disease and related myopathies in the C-terminal transmembrane region of the RYR1 gene

The congenital myopathies are a group of disorders characterised by the predominance of specific histological features observed in biopsied muscle. Central core disease and nemaline myopathy are examples of congenital myopathies that have specific histological characteristics but significantly overlapping clinical pictures. Central core disease is an autosomal dominant disorder with variable penetrance which has been linked principally to the gene for the skeletal muscle calcium release channel (RYR1). Two recent reports have identified the 3' transmembrane domain of this gene as a common site for mutations. Two other studies have reported single families that have features of both central core disease and nemaline myopathy (core/rod disease) caused by mutations in RYR1. Screening of the 3' region (exons 93-105) of the RYR1 gene for mutations in 27 apparently unrelated patients with either central core disease or core/rod disease by single strand conformation polymorphism analysis and DNA sequencing identified three described and nine novel mutations in 15 patients.

Autosomal recessive inheritance of RYR1 mutations in a congenital myopathy with cores

Central core disease (CCD) is a congenital myopathy due to dominant mutations in the skeletal muscle ryanodine receptor gene (RYR1). The authors report three patients from two consanguineous families with symptoms of a congenital myopathy, cores on muscle biopsy, and confirmed linkage to the RYR1 locus. Molecular genetic studies in one family identified a V4849I homozygous missense mutation in the RYR1 gene. This report suggests a congenital myopathy associated with recessive RYR1 mutations.

Monitoring land-use change effects on soil carbon in New Zealand: quantifying baseline soil carbon stocks

We designed a soil carbon monitoring system for New Zealand using country-specific land use and soil carbon information. The system pre-stratifies the country by soil type, climate, and land use. Soils were placed in six IPCC soil categories; Podzols were added as they are widespread throughout New Zealand. Temperature was stratified into two categories, each spanning 7 degrees C. Moisture categories were based on water balance, and included five categories. Temperature and moisture stratification was based on the USDA Soil Classification system. Land use (10 categories) was based on 1980s survey data. Overall, 39 combinations of these three factors (cells) described 93% of the New Zealand landscape. Geo-referenced soil carbon data (carbon concentration and bulk density) were used to quantify average soil carbon for each of the 39 cells. Aggregating the polygons gave an estimated 1990 soil carbon baseline of 1152+/-44, 1439+/-73, and 1602+/-167 Mt C (mean+/-S.D.) for the 0-0.1, 0.1-0.3, and 0.3-1.0 m depth increments (not including forest floor carbon). The system described could also be used to quantify equilibrium changes in soil C associated with land-use change if land use is updated periodically.

Future directions for epilepsy research

The authors propose that epilepsy research embark on a revitalized effort to move from targeting control of symptoms to strategies for prevention and cure. The recent advances that make this a realistic goal include identification of genes mutated in inherited epilepsy syndromes, molecular characterization of brain networks, better imaging of sites of seizure origin, and developments in seizure prediction by quantitative EEG analysis. Research directions include determination of mechanisms of epilepsy development, identification of genes for common epilepsy syndromes through linkage analysis and gene chip technology, and validation of new models of epilepsy and epileptogenesis. Directions for therapeutics include identification of new molecular targets, focal methods of drug delivery tied to EEG activity, gene and cell therapy, and surgical and nonablative therapies. Integrated approaches, such as coupling imaging with electrophysiology, are central to progress in localizing regions of epilepsy development in people at risk and better seizure prediction and treatment for people with epilepsy.

HIV in the CNS: pathogenic relationships to systemic HIV disease and other CNS diseases

Research on the pathogenesis of the human immunodeficiency virus (HIV) infection of the central nervous system (CNS) has reached a pivotal stage. While the incidence of HIV dementia appears to be declining, the prevalence of milder, yet debilitating, neuropsychological impairments may rise as individuals infected with HIV live longer. There are also concerns about CNS reservoirs of latently infected cells. Building upon progress in understanding HIV neuropathogenesis, the time is ideal to expand research on the interrelationships between the CNS and systemic HIV disease, and extend the boundaries of this research to the neuropathogenic similarities between HIV and other CNS inflammatory diseases. Neuropathogenic insights gained from these pursuits can spawn new treatment strategies for HIV/CNS disease as well as potentially other diseases of the nervous system.

A novel ryanodine receptor gene mutation causing both cores and rods in congenital myopathy

BACKGROUND

Central core disease (CCD) and nemaline rod myopathy are generally considered two genetically and histologically distinct disorders. CCD is defined by the presence of well-demarcated round cores within most myofibers. Nemaline rod myopathy is distinguished by the presence of characteristic nemaline bodies within myofibers. The simultaneous occurrence of both cores and rods in the same muscle biopsy has been described, but no gene mutations have been reported yet for this condition.

OBJECTIVE

To describe a family containing 16 affected individuals in six generations with an autosomal dominant congenital myopathy that shows clinical and histologic features of both CCD and nemaline myopathy, and to determine the genetic etiology and protein composition of the cores/rods in this family.

METHODS AND RESULTS

The results of linkage analyses excluded involvement of the two autosomal dominant nemaline myopathy loci on chromosome 1, but were consistent with a localization of the disease gene at the CCD locus on chromosome 19q13.1 (ryanodine receptor). SSCP analysis and DNA sequencing identified a novel Thr4637Ala mutation in the transmembrane region of the ryanodine receptor protein. Immunofluorescence studies of patient muscle biopsies showed the central cores to stain for ryanodine receptor.

CONCLUSIONS

These data suggest that the occurrence of nemaline bodies can be a secondary feature of CCD, and that genetic studies on previously reported core/rod families should be targeted to the ryanodine receptor locus. The results of the immunofluorescence studies suggest that the cores contain excess abnormal ryanodine receptor protein.

Metabolism of A dopamine D(4)-selective antagonist in rat, monkey, and humans: formation of A novel mercapturic acid adduct

3-([4-(4-Chlorophenyl)piperazin-1-yl]-methyl)-1H-pyrrolo-2, 3-beta-pyridine (L-745,870) is a dopamine D(4) selective antagonist that has been studied as a potential treatment for schizophrenia, with the expectation that it would not exhibit the extrapyramidal side effects often observed with the use of classical antipsychotic agents. The metabolism of L-745,870 in vivo was investigated in the rat, rhesus monkey, and human using liquid chromatography-tandem mass spectrometry and/or NMR techniques in conjunction with radiochemical detection. In all three species, two major metabolic pathways were identified, namely N-dealkylation at the substituted piperazine moiety and the formation of a novel mercapturic acid adduct. It is proposed that the latter biotransformation process involves the formation of an electrophilic imine methide intermediate, analogous to that produced from 3-methyl indole. This report appears to represent the first example of metabolic activation of a 3-alkyl-7-azaindole nucleus.

Identification of S-(n-butylcarbamoyl)glutathione, a reactive carbamoylating metabolite of tolbutamide in the rat, and evaluation of its inhibitory effects on glutathione reductase in vitro

Tolbutamide (TOLB), a widely used hypoglycemic agent in the therapy of non-insulin-dependent diabetes mellitus, has been reported to be teratogenic and/or embryotoxic in several animal species and humans. It has been proposed that the teratogenic effects of TOLB are linked to drug-mediated depletion of glutathione (GSH) through inhibition of the enzyme glutathione reductase (GR), although the mechanism by which this inhibition occurs remains unknown. In the study presented here, rats were injected with TOLB (200 mg/kg ip), and bile was collected for analysis by liquid chromatography/tandem mass spectrometry (LC/MS/MS). This led to the identification of S-(n-butylcarbamoyl)glutathione (SBuG), a reactive GSH conjugate derived from n-butyl isocyanate, as a minor metabolite of TOLB in bile. Upon incubation of SBuG (0.25-1.0 mM) with GR from either yeast or bovine intestinal mucosa in the presence of NADPH (0.20 mM), enzyme activity was lost in a time- and concentration-dependent manner. No inhibition was observed when NADPH was omitted from incubations, or when the natural substrate for the enzyme, glutathione disulfide (GSSG, 0.05 mM), was added. TOLB itself did not inhibit GR over the concentration range of 0.8-2.0 mM. It is concluded that metabolic activation of TOLB in vivo leads to the generation of reactive intermediates (n-butyl isocyanate and SBuG) which carbamoylate and thereby inhibit GR. At critical periods of organogenesis, the resulting perturbation of GSH homeostasis in exposed tissues may play a key role in the teratogenic and/or embryotoxic effects of TOLB.

Homozygosity for a nonsense mutation in the alpha-tropomyosin slow gene TPM3 in a patient with severe infantile nemaline myopathy

The nemaline myopathies are muscle disorders of variable severity and age of onset, with characteristic nemaline bodies in the sarcoplasm. Genes for dominant (NEM1) and recessive (NEM2A) nemaline myopathy have been localised to chromosomes one and two, respectively. A missense mutation in the alpha-tropomyosin gene (TPM3) has been associated with NEM1 in one family. Probands from 76 other nemaline myopathy families have now been screened for TPM3 mutations. One proband, who was not noted to have any weakness neonatally, but who died at 21 months of age, was shown to be homozygous for a single strand conformation polymorphism (SSCP) in skeletal-muscle-specific exon 1 of TPM3. Sequencing revealed homozygosity for a nonsense mutation at codon 31 (CAG to TAG). The patient should have no functioning alpha-tropomyosin slow protein. The nemaline bodies in this patient were exclusively in type one fibres, consistent with the expression of TPM3 only in type one fibres.

Using Airborne Digital Imagery for Detecting Oak Wilt Disease

Color-infrared (CIR) digital imagery was evaluated as a remote sensing tool for detecting oak wilt disease in live oak (Quercus fusiformis). Aerial CIR digital imagery and CIR photography were obtained concurrently of a live oak forested area in south-central Texas affected by oak wilt. Dead, diseased, and healthy live oak trees could generally be delineated as well in the digital imagery as in the CIR photography. Light reflectance measurements obtained in the field showed that dead, diseased, and healthy trees had different visible and near-infrared reflectance values.

Metabolic activation of diclofenac by human cytochrome P450 3A4: role of 5-hydroxydiclofenac

Cytochrome P450 2C11 in rats was recently found to metabolize diclofenac into a highly reactive product that covalently bound to this enzyme before it could diffuse away and react with other proteins. To determine whether cytochromes P450 in human liver could catalyze a similar reaction, we have studied the covalent binding of diclofenac in vitro to liver microsomes of 16 individuals. Only three of 16 samples were found by immunoblot analysis to activate diclofenac appreciably to form protein adducts in a NADPH-dependent pathway. Cytochrome P450 2C9, which catalyzes the major route of oxidative metabolism of diclofenac to produce 4'-hydroxydiclofenac, did not appear to be responsible for the formation of the protein adducts, because sulfaphenazole, an inhibitor of this enzyme, did not affect protein adduct formation. In contrast, troleandomycin, an inhibitor of P450 3A4, inhibited both protein adduct formation and 5-hydroxylation of diclofenac. These findings were confirmed with the use of baculovirus-expressed human P450 2C9 and P450 3A4. One possible reactive intermediate that would be expected to bind covalently to liver proteins was the p-benzoquinone imine derivative of 5-hydroxydiclofenac. This product was formed by an apparent metal-catalyzed oxidation of 5-hydroxydiclofenac that was inhibited by EDTA, glutathione, and NADPH. The p-benzoquinone imine decomposition product bound covalently to human liver microsomes in vitro in a reaction that was inhibited by GSH. In contrast, GSH did not prevent the covalent binding of diclofenac to human liver microsomes. These results suggest that for appreciable P450-mediated bioactivation of diclofenac to occur in vivo, an individual may have to have both high activities of P450 3A4 and perhaps low activities of other enzymes that catalyze competing pathways of metabolism of diclofenac. Moreover, the p-benzoquinone imine derivative of 5-hydroxydiclofenac probably has a role in covalent binding in the liver only under the conditions where levels of NADPH, GSH, and other reducing agents would be expected to be low.

Identification of in vitro metabolites of Indinavir by "intelligent automated LC-MS/MS" (INTAMS) utilizing triple quadrupole tandem mass spectrometry

In an effort to improve the efficiency of the TSQ 7000 LC-MS/MS system for identification of drug metabolites in biological matrices in support of drug discovery programs, a combination of instrument control language procedures for the Finnigan MAT TSQ 7000 mass spectrometer, referred to as INTAMS, were composed. INTAMS was designed to conduct unattended, automatic liquid chromatography/mass spectrometry (LC-MS) and LC-MS/MS analyses of drugs and metabolites in commonly encountered in vitro biological matrices. A novel peak detection algorithm was developed to automatically detect and record the pseudomolecular ions and retention times of chromatographic components, even if not fully resolved. This algorithm was used in combination with an automated technique for predicting the molecular weights of metabolites based on incremental changes of the molecular weight of the parent drug resulting from well-known biotransformation processes. When applied to a sample of an incubation mixture of the HIV protease inhibitor Indinavir with a rat liver S9 preparation, the results obtained by the automatic metabolite detection procedures for LC-MS and LC-MS/MS analyses in real time were the same as those which were determined manually, by a knowledgeable operator.

Identification of drug metabolites in biological matrices by intelligent automated liquid chromatography/tandem mass spectrometry

A rapid and systematic strategy for the identification of drug metabolites in biological matrices based on liquid chromatography-tandem mass spectrometry (LC/MS/MS) techniques was utilized for the identification of drug metabolites of the HIV protease inhibitor Indinavir. This strategy integrates intelligent realtime mass spectrometry with HPLC detection and a predictive strategy for detecting metabolites arising from common biotransformations, to rapidly elucidate structures of drug metabolites. Structures of metabolites generated from in vitro incubation mixtures of Indinavir were characterized from a single chromatographic analysis using the automated LC/MS/MS methodology, thus reducing data acquisition time and improving efficiency.

Alzheimer's disease and apolipoprotein E genotype in Western Australia: an autopsy-verified series

OBJECTIVE

To determine the relationship between the apolipoprotein E epsilon 4 allele and autopsy-verified Alzheimer's disease (AD) in an Australian population.

DESIGN

Retrospective case-control study.

SETTING

Royal Perth Hospital, Perth, Western Australia (a tertiary referral hospital).

SUBJECTS

50 subjects with "definite" AD (according to the histological and clinical criteria of the Consortium to Establish a Registry for Alzheimer's Disease [CERAD]) and 30 control subjects who had died from a non-neurological disease were randomly selected from the hospital's neuropathology register.

OUTCOME MEASURES

Histological grading of brain sections stained with the modified Bielschowsky stain according to the criteria of CERAD; number (burden) of neuritic plaques; apolipoprotein E genotype (APOE).

RESULTS

Frequency of the epsilon 4 allele was significantly higher in the AD group (37%) than in the control group (2%) (chi 2 = 25.8; P < 0.00001). In the AD group, 50% of subjects were heterozygous for the epsilon 4 allele and 12% were homozygous, while in the control group one subject was heterozygous for the allele and none were homozygous. No association was seen between the epsilon 4 allele and neuritic plaque burden in the hippocampus, entorhinal cortex, middle frontal gyrus or inferior parietal lobule in subjects with AD.

CONCLUSIONS

Our findings confirm an association between the epsilon 4 allele and autopsy-verified AD. The epsilon 4 allele may be an important risk factor for susceptibility to AD in the general Australian population.

Identification in rat bile of glutathione conjugates of fluoromethyl 2,2-difluoro-1-(trifluoromethyl)vinyl ether, a nephrotoxic degradate of the anesthetic agent sevoflurane

Recent studies have indicated that the nephrotoxicity of fluoromethyl 2,2-difluoro-1-(trifluoromethyl)vinyl ether ("Compound A"), a breakdown product of the inhaled anesthetic sevoflurane, may be mediated by a reactive intermediate(s) generated via the cysteine conjugate beta-lyase pathway. In order to gain a better understanding of glutathione (GSH)-dependent metabolism of Compound A, the present study was carried out with the primary goal of detecting and characterizing Compound A--GSH conjugates. By means of ionspray LC-MS/MS and NMR spectroscopy, a total of four GSH conjugates ("A1-A4") were identified from the bile of rats dosed intraperitoneally with Compound A. A1 and A2 were identified as two diastereomers of S-[1,1-difluoro-2-(fluoromethoxy)-2-(trifluoromethyl)ethyl]glutath ione, while A3 and A4 were identified as (E)- and (Z)-S-[1-fluoro-2-(fluoromethoxy)-2-(trifluoromethyl)-vinyl]glutat hione, respectively. Quantitative analyses indicated that approximately 29% of the administered dose of Compound A was excreted into the bile in the form of the above GSH conjugates over a period of 6 h. Studies conducted in vitro demonstrated that the reaction of Compound A with GSH was catalyzed by both rat liver cytosolic and microsomal glutathione S-transferases (GST), with the two enzyme systems exhibiting different product selectivities. Formation of these GSH conjugates also occurred nonenzymatically at an appreciable rate. These results indicate that spontaneous and enzyme-mediated conjugation with GSH represents a major pathway of metabolism of Compound A in rats. Conjugation of Compound A with GSH in vivo appeared to be catalyzed preferentially by microsomal rather than cytosolic GST, based on comparison of biliary, microsomal, and cytosolic metabolic profiles. By analogy with other haloalkenes, further metabolism of the corresponding cysteine conjugates of Compound A by renal cysteine conjugate beta-lyase may lead to the formation of reactive acylating agents, which would be expected to bind covalently to cellular macromolecules and cause organ-selective nephrotoxicity.

Enhanced production of bovine tumor necrosis factor-alpha during the periparturient period

This study examined the production of tumor necrosis factor (TNF-alpha) by mononuclear cells isolated from peripheral blood and supramammary lymph nodes of periparturient and mid to late lactating dairy cows. Monocyte-enriched cell populations were stimulated with lipopolysaccharide (LPS) and analyzed for TNF-alpha concentrations. Flow cytometric analysis was performed to determine the frequencies of relevant cell populations. Isolated mononuclear cells from periparturient dairy cows produced significantly higher levels of TNF-alpha than mid to late lactating dairy cows regardless of tissue location. A corresponding increase in the frequency of monocytes also was observed in tissue samples obtained from periparturient animals. The higher proportion of monocytes capable of producing TNF-alpha in the periparturient dairy cow may account for the increased levels of this potent mediator. Within the periparturient period, peripheral blood mononuclear cells were found to produce significantly less TNF-alpha than cells isolated from mammary lymph nodes. However, flow cytometric analysis revealed similar monocyte concentrations in both the peripheral blood and mammary lymph node. This indicates that the differences in cytokine production may be due to variations in monocyte activation state with respect to tissue location. It is possible that greater potential to produce TNF-alpha during the periparturient period may contribute to the severe acute phase response of the mammary gland to coliform infections during this time. Limiting TNF-alpha production by monocytes, particularly within the mammary gland, may reduce the severity of clinical coliform mastitis in periparturient dairy cattle.

Nephrotoxicity of sevoflurane compound A [fluoromethyl-2,2-difluoro-1-(trifluoromethyl)vinyl ether] in rats: evidence for glutathione and cysteine conjugate formation and the role of renal cysteine conjugate beta-lyase

Compound A, which is a breakdown product of the volatile anesthetic sevoflurane, is nephrotoxic in rats, although the mechanism of this toxicity is unknown. In the present investigation, the role of glutathione conjugation, glutathione conjugate processing to cysteine conjugates, and renal cysteine conjugate beta-lyase in the pathogenesis of Compound A nephrotoxicity was investigated in the rat. Following intraperitoneal administration of Compound A (1 mmol/kg), the presence of bile of two types of Compound A-glutathione conjugates, and the urinary excretion of two types of Compound A-mercapturic acid conjugates, was demonstrated by ionspray-tandem mass spectrometry. Aminooxyacetic acid, a competitive inhibitor of renal cysteine conjugate beta-lyase, partially protected against Compound A-induced diuresis and proteinuria. These results suggest that glutathione conjugate formation, subsequent processing to cysteine conjugates, and cysteine conjugate metabolism by renal beta-lyase may be important factors in the pathogenesis of Compound A-mediated nephrotoxicity in rats.

Patho- and immunobiology of malignant mesothelioma: characterisation of tumour infiltrating leucocytes and cytokine production in a murine model

Malignant mesothelioma (MM) is an aggressive, uniformly fatal serosal tumour, usually associated with asbestos exposure, for which there currently is no effective treatment. In order to gain insight into the mechanism(s) whereby MM might escape immune surveillance, a murine model for MM was used (a) to characterise the tumour-infiltrating lymphocytes (TIL) and macrophages (TIM) phenotypically, (b) to examine systemic immune recognition of MM, and (c) to examine the possible influence of tumour-derived cytokines on systemic and local pathobiological manifestations of MM. A profound down-regulation of lymphocyte surface markers, known to be involved in T cell activation, was found in TIL. Likewise, although TIM were present in large numbers, their expression of MHC class II antigen and integrins was weak or absent, suggestive of altered functional activity. Significant amounts of cytokines, in particular transforming growth factor beta, interleukin-6 (IL-6), IL-1 and tumour necrosis factor were produced during the course of MM tumour development-directly by the MM cells and/or indirectly in response to tumour growth. These factors may contribute both to derangement of antitumour effector mechanisms and to the clinical and pathological manifestations of the disease.

Identification of novel glutathione conjugates of disulfiram and diethyldithiocarbamate in rat bile by liquid chromatography-tandem mass spectrometry. Evidence for metabolic activation of disulfiram in vivo

Recent studies have shown that the inhibitory effects of disulfiram and diethyldithiocarbamate (DDTC) (to which disulfiram is rapidly reduced in vivo) on the liver mitochondrial low-Km form of aldehyde dehydrogenase (ALDH) may be mediated by a reactive metabolite(s) of these compounds. In order to investigate the nature of such electrophilic intermediates in vivo, the present study was carried out with the goal of detecting and identifying their respective glutathione (GSH) conjugates in the bile of rats dosed ip with either disulfiram (75 mg kg-1) or sodium DDTC (114 mg kg-1). By means of highly selective screening strategies based on coupled liquid chromatography-tandem mass spectrometry techniques, one major and four minor GSH adducts were identified as common biliary metabolites of disulfiram and DDTC. The major conjugate, whose excretion into bile over 4 h accounted for ca. 1% of the dose of either precursor, was identified as S-(N,N-diethylcarbamoyl)glutathione (SDEG). In vitro experiments with synthetic SDEG demonstrated that this carbamate thioester derivative is chemically stable in aqueous media under physiological conditions and does not carbamoylate nucleophiles such as cysteine. Consistent with these findings, SDEG failed to inhibit yeast ALDH in vitro. The minor GSH conjugates in bile were identified as S-(N,N-diethylthiocarbamoyl)glutathione, S-(N-ethyl-carbamoyl)glutathione, S-(N-ethylthiocarbamoyl)glutathione, and S-[N-(carboxymethyl)-N- ethylcarbamoyl]glutathione, the structures of which indicate that metabolic oxidation takes place at the thiono sulfur group and at each of the carbon atoms of disulfiram and DDTC.(ABSTRACT TRUNCATED AT 250 WORDS)

Metabolic activation of unsaturated derivatives of valproic acid. Identification of novel glutathione adducts formed through coenzyme A-dependent and -independent processes

The ability of 2-n-propyl-4-pentenoic acid (delta 4-VPA) and 2-n-propyl-2(E)-pentenoic acid ([E]-delta 2-VPA), two unsaturated metabolites of valproic acid (VPA), to form reactive intermediates, deplete hepatic glutathione (GSH) and cause accumulation of liver triglycerides was investigated in the rat. With the aid of ionspray liquid chromatography-tandem mass spectrometry (LC-MS/MS), three GSH adducts were detected in the bile of delta 4-VPA-treated animals and were identified as 4-hydroxy-5-glutathion-S-yl-VPA-gamma-lactone, 5-glutathion-S-yl-(E)-delta 3-VPA and 3-oxo-5-glutathion-S-yl-VPA. A fourth conjugate was identified tentatively as 4-glutathion-S-yl-5-hydroxy-VPA. Quantitative analysis of the corresponding N-acetyl-cysteine (NAC) conjugates in urine indicated that metabolism of delta 4-VPA via the GSH-dependent pathways accounted for approximately 20% of an acute dose (100 mg kg-1 i.p.). In contrast, when rats were given an equivalent dose of (E)-delta 2-VPA, only one GSH adduct (5-glutathion-S-yl-(E)-delta 3-VPA) was detected at low concentrations in bile. In vitro experiments with rat liver mitochondria demonstrated that delta 4-VPA undergoes coenzyme A- and ATP-dependent metabolic activation in this organelle via the beta-oxidation pathway to intermediates which bind covalently to proteins. When liver homogenates and hepatic mitochondria from rats injected with delta 4-VPA, (E)-delta 2-VPA or VPA were analyzed for GSH content, it was found that only delta 4-VPA depleted GSH pools significantly. Treatment of rats with delta 4-VPA and (to a lesser extent) VPA led to an accumulation of liver triglycerides, whereas (E)-delta 2-VPA had no measurable effect. It is concluded that delta 4-VPA undergoes metabolic activation by both microsomal cytochrome P-450-dependent and mitochondrial coenzyme A-dependent processes, and that the resulting electrophilic intermediates, which are trapped in part by GSH, may mediate the hepatotoxic effects of this compound. In contrast, (E)-delta 2-VPA is not transformed to any appreciable extent to reactive metabolites, which thus accounts for the apparent lack of hepatotoxicity of this positional isomer in the rat.

Effect of antecedent hypoglycemia on cognitive function and on glycemic thresholds for counterregulatory hormone secretion in healthy humans

OBJECTIVE

To determine whether reduced hormonal, symptomatic, and/or cognitive responses to hypoglycemia are caused by an increase in the plasma glucose concentration required to stimulate these counterregulatory parameters after antecedent hypoglycemia.

RESEARCH DESIGN AND METHODS

We studied nine healthy volunteers during stepped hypoglycemia clamps (plasma glucose targets from 80 to 50 mg/dl in 10 mg/dl steps) on two separate days. The study was preceded either by a 2-h period of hypoglycemia (plasma glucose 58 +/- 2 mg/dl) or a 2-h period of euglycemia (plasma glucose 94 +/- 2 mg/dl) for 90 min.

RESULTS

The plasma glucose that triggered secretion of plasma norepinephrine (NE) was lower after antecedent hypoglycemia (control = 74 +/- 2 and experimental = 67 +/- 2 mg/dl, respectively, P < 0.005). In contrast, a relatively higher plasma glucose stimulated secretion of other counterregulatory hormones after antecedent hypoglycemia: growth hormone (GH) (65 +/- 2 to 72 +/- 2 mg/dl, P < 0.01); glucagon (63 +/- 2 to 70 +/- 2 mg/dl, P < 0.01); and epinephrine (EPI) (68 +/- 2 to 76 +/- 2 mg/dl, P < 0.01) when comparing control days with experimental days. Hypoglycemic symptoms were first observed at a plasma glucose plateau of 59 +/- 2 mg/dl. Motor function reflected by Digit Symbol Substitution deteriorated equally whether there had been antecedent hypoglycemia or euglycemia. Logical (immediate) memory deteriorated in the control study at a plasma glucose of 54 +/- 2 mg/dl but remained unchanged at equivalent hypoglycemia in the experimental study (P < 0.03).

CONCLUSIONS

Our conclusions are as follows: 1) symptoms of moderate hypoglycemia occur at plasma glucose levels averaging approximately 5-15 mg/dl lower than the plasma glucose concentrations required to trigger counterregulatory hormone release; 2) after acute antecedent hypoglycemia, glucagon, EPI, and GH secretion occur at higher plasma glucose concentrations and NE is released at lower plasma glucose concentrations; and 3) there may be CNS adaptation to prior hypoglycemia reflected in preservation of logical memory function at plasma glucose levels of approximately 50 mg/dl. These findings suggest that thresholds for hormone secretion and for changes in cognitive function can be altered very acutely by foregoing hypoglycemia in healthy humans.

Physiologic hyperinsulinemia enhances counterregulatory hormone responses to hypoglycemia in IDDM

We evaluated the effect of physiologic hyperinsulinemia (plasma insulin 329 +/- 62 vs 687 +/- 62 pmol/L) on counterregulatory hormone responses in 8 IDDM subjects studied during a 2-hour hypoglycemic clamp study with an equivalent degree of hypoglycemia (plasma glucose 3.1 +/- 0.1 and 3.0 +/- 0.1 mmol/L, respectively). Plasma epinephrine levels were increased by 71% during the last 60 minutes of hypoglycemia in the high insulin study (840 +/- 180 vs 1440 +/- 310 pmol/L, respectively p = 0.006). In addition, plasma cortisol and norepinephrine were also increased in the high insulin study (by 19% and 24% respectively, p < 0.01, for both). Plasma growth hormone and glucagon concentrations were not altered by high dose insulin infusion. In spite of increased epinephrine secretion, the glucose infusion rate required to maintain glucose was 2-fold greater in the high insulin study, and there was greater suppression of lipolysis in that group. We conclude that hyperinsulinemia may enhance counterregulatory hormone secretion in IDDM.

Studies on the metabolic fate of caracemide, an experimental antitumor agent, in the rat. Evidence for the release of methyl isocyanate in vivo

Following administration to rats of a single ip dose (6.6 mg kg-1) of the investigational antitumor agent caracemide (N-acetyl-N,O-bis[methylcarbamoyl]hydroxylamine), the mercapturic acid derivative N-acetyl-S-(N-methylcarbamoyl)cysteine (AMCC) was identified in urine by thermospray LC-MS. Quantification of this conjugate was carried out by stable isotope dilution thermospray LC-MS, which indicated that the fraction of the caracemide dose recovered as AMCC in 24-h urine collections was 54.0 +/- 5.5% (n = 4). Since AMCC is known to represent a major urinary metabolite of methyl isocyanate (MIC) in the rat, the results of this study support the contention that caracemide yields MIC as a toxic intermediate in vivo. Furthermore, with the aid of a specifically deuterium-labeled analog of caracemide ([carbamoyloxy-C2H3]caracemide), it was shown that the methylcarbamoyl group of AMCC derived from both the O-methylcarbamoyl (72%) and N-methylcarbamoyl (28%) side chains of the drug. In view of these findings, it is concluded that caracemide acts as a latent form of MIC in vivo and that this reactive isocyanate (or labile S-linked conjugates thereof) may contribute to the antitumor properties and/or adverse side-effects of caracemide.

Glutathione and N-acetylcysteine conjugates of 2-chloroethyl isocyanate. Identification as metabolites of N,N'-bis(2-chloroethyl)-N-nitrosourea in the rat and inhibitory properties toward glutathione reductase in vitro

The antitumor agent N,N'-bis(2-chloroethyl)-N-nitrosourea (BCNU) is known to be unstable in aqueous solution, and to degrade spontaneously to reactive alkylating and carbamoylating intermediates. Whereas the alkylating component is believed to be responsible for the antitumor effects of this drug, it has been speculated that the carbamoylating species 2-chloroethyl isocyanate (CEIC) may mediate some of the serious adverse effects of BCNU therapy. In order to determine whether CEIC is released from BCNU in vivo, rats were administered an ip injection of the drug and a targeted search was made by ionspray LC-MS/MS techniques for the glutathione (GSH) conjugate of CEIC in bile and for the corresponding N-acetylcysteine (NAC) adduct in urine. Both of these S-linked conjugates were identified on the basis of their HPLC and MS/MS characteristics, which were identical to those of the respective reference compounds prepared by synthesis. Quantitative studies indicated that, following an ip dose of BCNU (24 mg kg-1), excretion of the GSH conjugate in bile over 4 h accounted for 3.90 +/- 0.64% of the administered dose, while excretion of the mercapturic acid derivative in urine over 24 h accounted for a further 18.1 +/- 3.3% (n = 4). Experiments conducted in vitro demonstrated that the S-linked conjugates of CEIC were of limited stability under simulated physiological conditions, decomposing to generate free GSH and NAC. In addition, both adducts inhibited rat liver glutathione reductase in vitro, when they were essentially equipotent to BCNU.(ABSTRACT TRUNCATED AT 250 WORDS)

Establishment of a murine model of malignant mesothelioma

Malignant mesothelioma (MM) is an aggressive tumour of the serosal cavities which is associated with previous asbestos exposure and is generally found to be resistant to conventional forms of therapy. Adequate scientific and clinical assessment of this disease has been severely limited by the relatively low incidence of mesothelioma and the lack of representative cell lines and animal models. The purpose of this study was to develop an asbestos-induced murine model of MM both as an in vivo-passaged malignancy and as in vitro-established cell lines. Such a model system would be invaluable for use in the study of various cellular, molecular and genetic aspects of the disease, and for the pre-clinical evaluation of potential therapeutic agents. BALB/c and CBA mice were injected intraperitoneally with crocidolite asbestos. Seven to 25 months after exposure, 35% of the mice developed mesothelioma (5 BALB/c, 9 CBA), as determined by standard cytological and histological parameters. From these primary tumours, 12 continuously growing cell lines (5 BALB/c, 7 CBA) were established in culture. All have been confirmed as mesothelioma by cytological and ultrastructural (electron microscopy) analyses. These lines have been in culture for 7 to 24 months and have achieved passages above 32 (range 32 to 106). As in the human disease, the murine mesothelioma lines vary in their morphology and growth rates (doubling times ranging from 14 to 30 hr). All cell lines produced tumours when injected into syngeneic mice.