Functional Pdgfra fibroblast heterogeneity in normal and fibrotic mouse lung

Aberrant fibroblast function plays a key role in the pathogenesis of idiopathic pulmonary fibrosis, a devastating disease of unrelenting extracellular matrix deposition in response to lung injury. Platelet-derived growth factor α-positive (Pdgfra+) lipofibroblasts (LipoFBs) are essential for lung injury response and maintenance of a functional alveolar stem cell niche. Little is known about the effects of lung injury on LipoFB function. Here, we used single-cell RNA-Seq (scRNA-Seq) technology and PdgfraGFP lineage tracing to generate a transcriptomic profile of Pdgfra+ fibroblasts in normal and injured mouse lungs 14 days after bleomycin exposure, generating 11 unique transcriptomic clusters that segregated according to treatment. While normal and injured LipoFBs shared a common gene signature, injured LipoFBs acquired fibrogenic pathway activity with an attenuation of lipogenic pathways. In a 3D organoid model, injured Pdgfra+ fibroblast-supported organoids were morphologically distinct from those cultured with normal fibroblasts, and scRNA-Seq analysis suggested distinct transcriptomic changes in alveolar epithelia supported by injured Pdgfra+ fibroblasts. In summary, while LipoFBs in injured lung have not migrated from their niche and retain their lipogenic identity, they acquire a potentially reversible fibrogenic profile, which may alter the kinetics of epithelial regeneration and potentially contribute to dysregulated repair, leading to fibrosis.

Surgical repair of a meningoencephalocoele in a kākāpō (Strigops habroptilus)

CASE HISTORY

A kākāpō (Strigops habroptilus) chick hatched on an off-shore island of New Zealand with a small white mass protruding through the cranial skin of the head. The chick's growth followed a normal pattern for kākāpō but at 3 weeks of age the cranium mass was non-reducible and fixed in place and the chick was removed from the island for diagnostic imaging and hand-rearing.

CLINICAL FINDINGS AND TREATMENT

A computed tomography (CT) examination revealed a full-thickness circular defect in the central cranium with suspected herniation of brain and dura. Surgery was performed at 37 days of age, and the herniated dura was dissected from the open fontanelle. Attempts to reduce the herniated tissue were unsuccessful, so the herniated dura and cortex were clamped and resected. The dura was closed and the periosteum of the skull was scarified and monofilament polypropylene mesh was secured tautly over the fontanelle. The mesh graft was infused with autologous bone marrow harvested from the ulna in an attempt to stimulate osteogenesis in the mesh repair. The skin flap was then closed. Post-operative recovery and healing were without complication. A CT examination 4 weeks after surgery showed no recurrence of the hernia, and a composite of mesh and scar over the open fontanelle which had reduced in diameter. The chick was released back onto an off-shore island with a radio transmitter and it continues to be monitored regularly.

PATHOLOGICAL FINDINGS

The tissue resected at surgery consisted of a cylindrical core of cerebral parenchyma overlain by a mildly hyperplastic epidermis, and large amounts of oedematous fibrovascular tissue arising from the leptomeninges.

DIAGNOSIS

Rostral parietal meningoencephalocoele.

CLINICAL RELEVANCE

This is the first report of successful surgical resolution of a meningoencephalocoele in any bird. Techniques from human neurosurgery were adapted for the unique anatomical features of the avian skull. The risks of the procedure included increased intra-cranial pressure resulting in anaesthetic complications or death, cerebrospinal fluid leakage, meningitis or recurrence of the meningoencephalocoele. In the longer term, there was a risk of developmental deficits in cognition or behaviour. None of these complications eventuated in the short to medium term, probably due to the small size of the meningoencephalocoele.

A mesoscale finite element modeling approach for understanding brain morphology and material heterogeneity effects in chronic traumatic encephalopathy

Chronic Traumatic Encephalopathy (CTE) affects a significant portion of athletes in contact sports but is difficult to quantify using clinical examinations and modeling approaches. We use an in silico approach to quantify CTE biomechanics using mesoscale Finite Element (FE) analysis that bridges with macroscale whole head FE analysis. The sulci geometry produces complex stress waves that interact with one another to create increased shear stresses at the sulci depth that are significantly larger than in analyses without sulci (from 0.5 to 18.0 kPa). Sulci peak stress concentration regions coincide with experimentally observed CTE sites documented in the literature. HighlightsSulci introduce stress localizations at their depth in the gray matterSulci stress fields interact to produce stress concentration sites in white matterDifferentiating brain tissue properties did not significantly affect peak stresses.

Mass spectrometric identification of candidate RNA-binding proteins associated with Transition Nuclear Protein mRNA in the mouse testis

Spermatogenesis is a differentiation process that requires dramatic changes to DNA architecture, a process governed in part by Transition Nuclear Proteins 1 and 2 (TNP1 and TNP2). Translation of Tnp1 and Tnp2 mRNAs is temporally disengaged from their transcription. We hypothesized that RNA regulatory proteins associate specifically with Tnp mRNAs to control the delayed timing of their translation. To identify potential regulatory proteins, we isolated endogenous mRNA/protein complexes from testis extract and identified by mass spectrometry proteins that associated with one or both Tnp transcripts. Five proteins showed strong association with Tnp transcripts but had low signal when Actin mRNA was isolated. We visualized the expression patterns in testis sections of the five proteins and found that each of the proteins was detected in germ cells at the appropriate stages to regulate Tnp RNA expression.

ICTV virus taxonomy profile: Sarthroviridae

The family Sarthroviridae includes a single genus, Macronovirus, which in turn includes a single species, Macrobrachium satellite virus 1. Members of this species, named extra small virus, are satellite viruses of Macrobrachium rosenbergii nodavirus, an unclassified virus related to members of the family Nodaviridae. Both viruses have isometric, spherical virions, infect giant freshwater prawns and together cause white tail disease, which is responsible for mass mortalities and severe economic losses in hatcheries and farms. Infection is caused by both vertical and horizontal transmission of virus. Aquatic insects act as a carrier to transmit the disease in prawns. This is a summary of the International Committee on Taxonomy of Viruses (ICTV) Report on the taxonomy of the Sarthroviridae, which is available at www.ictv.global/report/sarthroviridae.

Optimal reference genes for RT-qPCR normalization in the newborn

It is difficult to identify reliable reference genes for transcriptomic analyses in biofluids such as saliva. This situation is particularly relevant for the newborn population, where rapid development is associated with dynamic changes in gene expression. Real-time gene expression monitoring holds great promise for elucidating disrupted pathways that result in morbidities unique to this population, such as retinopathy of prematurity, but its impact depends on identifying stable and consistently expressed genes across a wide range of gestational ages. We extracted total RNA from 400 neonatal saliva samples (postconceptional ages: 32 5/7 to 48 2/7 weeks), converted it to cDNA, and pre-amplified and analyzed it by qPCR for three commonly used reference genes, ACTB, GAPDH, and YWHAZ. Relative quantification was determined using the Δ Ct method. Data were analyzed as a whole and also stratified by age and sex. Descriptive statistics and homogeneity of variance were performed to identify optimal reference genes. Data analyzed from all ages and both sexes showed significant expression variation for ACTB, while GAPDH and YWHAZ showed greater stability. Male infants exhibited increased expression variation compared to females for ACTB, but neither GAPDH nor YWHAZ showed significant variance for either sex. We suggest that ACTB is an unreliable reference gene for the newborn population. Males showed significantly more variation in ACTB expression compared to females, which suggests a sex-specific developmental role for this biomarker. By contrast, GAPDH and YWHAZ were less variable and therefore preferable for use in neonates. Our findings may improve the use of reference genes for the RT-qPCR platform in the newborn over a wide range of gestational ages, thereby minimizing the likelihood of erroneous interpretation of gene expression during rapid growth, development, and differentiation.

Leading indicators of community-based violent events among adults with mental illness

BACKGROUND

The public health, public safety and clinical implications of violent events among adults with mental illness are significant; however, the causes and consequences of violence and victimization among adults with mental illness are complex and not well understood, which limits the effectiveness of clinical interventions and risk management strategies. This study examined interrelationships between violence, victimization, psychiatric symptoms, substance use, homelessness and in-patient treatment over time.

METHOD

Available data were integrated from four longitudinal studies of adults with mental illness. Assessments took place at baseline, and at 1, 3, 6, 9, 12, 15, 18, 24, 30 and 36 months, depending on the parent studies' protocol. Data were analysed with the autoregressive cross-lag model.

RESULTS

Violence and victimization were leading indicators of each other and affective symptoms were a leading indicator of both. Drug and alcohol use were leading indicators of violence and victimization, respectively. All psychiatric symptom clusters - affective, positive, negative, disorganized cognitive processing - increased the likelihood of experiencing at least one subsequent symptom cluster. Sensitivity analyses identified few group-based differences in the magnitude of effects in this heterogeneous sample.

CONCLUSIONS

Violent events demonstrated unique and shared indicators and consequences over time. Findings indicate mechanisms for reducing violent events, including trauma-informed therapy, targeting internalizing and externalizing affective symptoms with cognitive-behavioral and psychopharmacological interventions, and integrating substance use and psychiatric care. Finally, mental illness and violence and victimization research should move beyond demonstrating concomitant relationships and instead focus on lagged effects with improved spatio-temporal contiguity.

Moisture, anisotropy, stress state, and strain rate effects on bighorn sheep horn keratin mechanical properties

This paper investigates the effects of moisture, anisotropy, stress state, and strain rate on the mechanical properties of the bighorn sheep (Ovis Canadensis) horn keratin. The horns consist of fibrous keratin tubules extending along the length of the horn and are contained within an amorphous keratin matrix. Samples were tested in the rehydrated (35wt% water) and ambient dry (10wt% water) conditions along the longitudinal and radial directions under tension and compression. Increased moisture content was found to increase ductility and decrease strength, as well as alter the stress state dependent nature of the material. The horn keratin demonstrates a significant strain rate dependence in both tension and compression, and also showed increased energy absorption in the hydrated condition at high strain rates when compared to quasi-static data, with increases of 114% in tension and 192% in compression. Compressive failure occurred by lamellar buckling in the longitudinal orientation followed by shear delamination. Tensile failure in the longitudinal orientation occurred by lamellar delamination combined with tubule pullout and fracture. The structure-property relationships quantified here for bighorn sheep horn keratin can be used to help validate finite element simulations of ram's impacting each other as well as being useful for other analysis regarding horn keratin on other animals.

STATEMENT OF SIGNIFICANCE

The horn of the bighorn sheep is an anisotropic composite composed of keratin that is highly sensitive to moisture content. Keratin is also found in many other animals in the form of hooves, claws, beaks, and feathers. Only one previous study contains high rate experimental data, which was performed in the dry condition and only in compression. Considering the bighorn sheep horns' protective role in high speed impacts along with the moisture and strain rate sensitivity, more high strain rate data is needed to fully characterize and model the material. This study provides high strain rate results demonstrating the effects of moisture, anisotropy, and stress state. As a result, the comprehensive data allows modeling efforts to be greatly improved.

The Effect of the Elapsed Time Between Blood Draw and Processing on the Recovery of Fetal Cells From Maternal Blood

OBJECTIVE

To test the hypothesis that a delay in initial fetal cell enrichment processing of maternal blood samples (defined as the time between blood draw and the initial density gradient centrifugation step) compromises the ability to recover fetal cells, we performed a randomized comparison of immediate (within 4 hours of draw) versus delayed (between 18-24 hours of draw) processing.

METHODS

Four centers participated: two centers utilized flow cytometry (FLOW), and two centers utilized magnetic-activated cell sorting (MACS) techniques. Each center collected 34 samples. The outcome was the percentage of gamma positive (gamma(+)) cells for FLOW or the number of nucleated red blood cells (NRBCs) for MACS, found in the final enriched cell population. Both outcomes reflect cell properties that are potentially fetal in origin, thus making them representative of the ability to recover fetal cells.

RESULTS

Our results did not support our hypothesis that delay in processing compromises fetal cell recovery. Instead, in MACS processing, we observed an increase in recovered NRBCs when blood sample processing was delayed compared with immediate processing. There was no significant difference in gamma(+) cells with FLOW.

CONCLUSION

Time-related changes in the density of target cells, perhaps associated with their progress towards apoptosis during the delay period, may result in increased intact fetal cells with the study methods utilized.

The Strength of Surfaces in Rolling Contact

The common engineering applications of rolling contact are reviewed: the wheel, rolling bearings, traction drives, gears and cams. It is shown that increasing the rigidity of the materials and decreasing the conformity of the surfaces reduces the resistance to rolling, but only at the expense of higher contact stress. The principal modes of failure are described: plastic deformation, contact fatigue, wear, scuffing and corrugation. Recent research into plastic deformation and fatigue is discussed. It is concluded that, if wear and scuffing are controlled by adequate lubrication and surface finish, and clean steel is used, the load capacity and life are governed by the nucleation of micro shear cracks through the action of cyclic plastic deformation.

Enhanced Approaches for Identifying Amadori Products: Application to Peanut Allergens

The dry roasting of peanuts is suggested to influence allergic sensitization as a result of the formation of advanced glycation end products (AGEs) on peanut proteins. Identifying AGEs is technically challenging. The AGEs of a peanut allergen were probed with nano-scale liquid chromatography-electrospray ionization-mass spectrometry (nanoLC-ESI-MS) and tandem mass spectrometry (MS/MS) analyses. Amadori product ions matched to expected peptides and yielded fragments that included a loss of three waters and HCHO. As a result of the paucity of b and y ions in the MS/MS spectrum, standard search algorithms do not perform well. Reactions with isotopically labeled sugars confirmed that the peptides contained Amadori products. An algorithm was developed on the basis of information content (Shannon entropy) and the loss of water and HCHO. Results with test data show that the algorithm finds the correct spectra with high precision, reducing the time needed to manually inspect data. Computational and technical improvements allowed for better identification of the chemical differences between modified and unmodified proteins.

Comparative performance analyses of commercially available products for salivary collection and nucleic acid processing in the newborn

Analysis of saliva for clinical monitoring and biomarker detection holds great promise for improving health care. Commercially available assays are not intended for use with neonates, however, and collection and processing of saliva for subsequent transcriptomic analysis presents unique challenges in this population. We compared RNA yield, quality, stability and RT-qPCR performance for two commonly used commercial systems: the Qiagen RNeasy Protect Saliva Mini Kit(®) and the DNA Genotek Oragene•RNA(®) assay. Two 10 μl saliva samples were collected from ten newborns and stabilized for each assay. Total RNA was extracted following incubation for 3, 10, 15 or 20 days. Total RNA extracted from each assay was analyzed for integrity, quality and quantity using the Agilent BioAnalyzer 2100. RT-qPCR was performed for the reference gene, GAPDH, to assess subsequent performance of the extracted RNA. Although the DNA Genotek extraction protocol required nearly twice the time of the Qiagen protocol, RNA integrity did not differ between the kits. RNA concentration using the DNA Genotek assay, however, was 3,264 pg/μl (range: 262 - 10,336 pg/μl) compared to 822.4 pg/μl (range: 0 - 1,856 pg/μl) for the Qiagen protocol. Linear regression analysis showed a stronger correlation between the threshold cycle and RNA concentration using DNA Genotek (r(2) = 0.356) compared to Qiagen (r(2) = 0.0331). Our results suggest that although the Qiagen assay may reduce overall extraction time, RNA yield and performance in subsequent transcriptomic analysis is more robust using the DNA Genotek assay.

Geometric effects on stress wave propagation

The present study, through finite element simulations, shows the geometric effects of a bioinspired solid on pressure and impulse mitigation for an elastic, plastic, and viscoelastic material. Because of the bioinspired geometries, stress wave mitigation became apparent in a nonintuitive manner such that potential real-world applications in human protective gear designs are realizable. In nature, there are several toroidal designs that are employed for mitigating stress waves; examples include the hyoid bone on the back of a woodpecker's jaw that extends around the skull to its nose and a ram's horn. This study evaluates four different geometries with the same length and same initial cross-sectional diameter at the impact location in three-dimensional finite element analyses. The geometries in increasing complexity were the following: (1) a round cylinder, (2) a round cylinder that was tapered to a point, (3) a round cylinder that was spiraled in a two dimensional plane, and (4) a round cylinder that was tapered and spiraled in a two-dimensional plane. The results show that the tapered spiral geometry mitigated the greatest amount of pressure and impulse (approximately 98% mitigation) when compared to the cylinder regardless of material type (elastic, plastic, and viscoelastic) and regardless of input pressure signature. The specimen taper effectively mitigated the stress wave as a result of uniaxial deformational processes and an induced shear that arose from its geometry. Due to the decreasing cross-sectional area arising from the taper, the local uniaxial and shear stresses increased along the specimen length. The spiral induced even greater shear stresses that help mitigate the stress wave and also induced transverse displacements at the tip such that minimal wave reflections occurred. This phenomenon arose although only longitudinal waves were introduced as the initial boundary condition (BC). In nature, when shearing occurs within or between materials (friction), dissipation usually results helping the mitigation of the stress wave and is illustrated in this study with the taper and spiral geometries. The combined taper and spiral optimized stress wave mitigation in terms of the pressure and impulse; thus providing insight into the ram's horn design and woodpecker hyoid designs found in nature.

Chorionic plate expression patterns of the maspin tumor suppressor protein in preeclamptic and egg donor placentas

Maspin is a serine protease inhibitor involved in regulating human placental trophoblast cell migration. Maspin has not been studied in preeclampsia (PE) or relative to the maternal-fetal immunological relationship, both of which may involve altered trophoblast migration. We examined maspin expression in placentas from in vitro fertilization (IVF) and egg donor (ED) pregnancies with and without PE. Exclusive to the chorionic plate, the number of maspin-positive extravillous trophoblasts was significantly decreased in IVF-PE vs. IVF (p = 0.005) and ED vs. IVF (p = 0.013). These data suggest maspin expression may be influenced by PE and/or the immunological dynamics of pregnancy.

Efficacy of a Nonpathogenic Acidovorax citrulli Strain as a Biocontrol Seed Treatment for Bacterial Fruit Blotch of Cucurbits

Bacterial fruit blotch (BFB), caused by the seedborne, gram-negative bacterium Acidovorax citrulli, is a serious threat to cucurbit seed and fruit production worldwide. Because of the lack of effective management strategies, we investigated the efficacy of a nonpathogenic A. citrulli strain as a biological control seed treatment for BFB. For this study, we generated a type III secretion system mutant of A. citrulli, AAC00-1ΔhrcC, that was nonpathogenic on watermelon but retained its ability to colonize germinating watermelon seed. With watermelon seed naturally infested with A. citrulli, AAC00-1ΔhrcC reduced BFB seedling transmission by 81.8% relative to control seed. In comparison, another A. citrulli antagonist, A. avenae strain AAA 99-2, reduced BFB seedling transmission by 74.6% for seed samples from the same lot. Additionally, when female watermelon blossoms were protected with AAC00-ΔhrcC and subsequently challenged with AAC00-1, the resulting seedlots displayed 8% BFB seedling transmission. This was not significantly different than seed from blossoms protected with AAA 99-2 (4%) but significantly less than those from blossoms protected with 0.1 M phosphate-buffered saline (36%). These results suggest that nonpathogenic A. citrulli has potential as a biological control seed treatment component in a comprehensive BFB management program.

Pregnancy-associated progenitor cells: an under-recognized potential source of stem cells in maternal lung

Novel therapies are needed for the treatment of acute and chronic lung diseases, many of which are incurable. The use of exogenous stem cells has shown promise in both animal models and clinical trials. However, to date, the stem cell literature has under-recognized naturally acquired pregnancy-associated progenitor cells (PAPCs). These cells are found at sites of injury or disease in female tissues. They persist for decades after parturition in maternal blood and organs, with the largest number being found in the maternal lungs. Their presence there may be one explanation for the sex differences observed in the prevalence and prognosis of some lung diseases. Although the clinical significance of these cells is as yet unknown, the literature suggests that some of the PAPCs are stem cells or have stem cell-like properties. PAPCs harvested from the blood or organs of parous women could potentially be used as an alternate source of cells with regenerative properties for the woman herself or her children. Because PAPCs preferentially traffic to the maternal lung they may play a significant role in recovery or protection from lung disease. In this review article, we discuss ongoing research investigating the administration of both adult and placenta-derived stem cells to treat lung disease, and how PAPCs may also play an important future therapeutic role.

Identification and functional characterization of a novel acetylcholine-binding protein from the marine annelid Capitella teleta

We identified a homologue of the molluscan acetylcholine-binding protein (AChBP) in the marine polychaete Capitella teleta, from the annelid phylum. The amino acid sequence of C. teleta AChBP (ct-AChBP) is 21-30% identical with those of known molluscan AChBPs. Sequence alignments indicate that ct-AChBP has a shortened Cys loop compared to other Cys loop receptors, and a variation on a conserved Cys loop triad, which is associated with ligand binding in other AChBPs and nicotinic ACh receptor (nAChR) alpha subunits. Within the D loop of ct-AChBP, a conserved aromatic residue (Tyr or Trp) in nAChRs and molluscan AChBPs, which has been implicated directly in ligand binding, is substituted with an isoleucine. Mass spectrometry results indicate that Asn122 and Asn216 of ct-AChBP are glycosylated when expressed using HEK293 cells. Small-angle X-ray scattering data suggest that the overall shape of ct-AChBP in the apo or unliganded state is similar to that of homologues with known pentameric crystal structures. NMR experiments show that acetylcholine, nicotine, and alpha-bungarotoxin bind to ct-AChBP with high affinity, with K(D) values of 28.7 microM, 209 nM, and 110 nM, respectively. Choline bound with a lower affinity (K(D) = 163 microM). Our finding of a functional AChBP in a marine annelid demonstrates that AChBPs may exhibit variations in hallmark motifs such as ligand-binding residues and Cys loop length and shows conclusively that this neurotransmitter binding protein is not limited to the phylum Mollusca.

Setting the agenda for multiple sclerosis rehabilitation research

BACKGROUND

Recognizing the need for more evidence-based multiple sclerosis (MS) rehabilitation, in the mid-2000s several initiatives were undertaken to explore why there had been a paucity of such research and to determine strategies to reverse this pattern. EXPERT-OPINION-PAPER: In 2004 the National Multiple Sclerosis Society (NMSS) convened an expert opinion panel, reviewed evidence-based MS rehabilitation research, and published the paper on the web. It was concluded that much of the MS rehabilitation carried out was based on experience, with little research backing it up.

INCREASING THE QUALITY AND QUANTITY OF MS REHABILITATION RESEARCH

Largely as a result of the conclusions of the Expert-Opinion-Paper, the NMSS convened a conference of a large number of MS and rehabilitation experts in New York in May, 2005. This conference made many recommendations of ways to increase the quantity and quality of MS research.

STATE OF THE SCIENCE CONFERENCE

In September, 2006, a follow-up conference was held in Washington, D.C... This conference, primarily sponsored by the University of Washington Multiple Sclerosis Rehabilitation Research and Training Center (MS RRTC), focused on some of the under-studied "hidden" disabilities present in persons with MS. This paper discusses the details and recommendations of these latter two conferences.

Prevalence of sleep problems in individuals with multiple sclerosis

BACKGROUND

Sleep disturbance in multiple sclerosis has received little research attention despite the potential influence it may have on disease impact.

OBJECTIVE

To estimate the prevalence of sleep disorders in a large community sample of individuals with multiple sclerosis.

METHODS

A cross-sectional self-report survey of 1063 persons with multiple sclerosis. Sleep was assessed using the Women's Health Initiative Insomnia Rating Scale and Medical Outcomes Study Sleep measure.

RESULTS

The prevalence of sleep problems in multiple sclerosis is significantly higher than in the general population or other chronic diseases and may affect women with multiple sclerosis more than men.

CONCLUSION

Sleep disturbance should routinely be evaluated in patients with multiple sclerosis and new interventions developed.

Mass spectrometry and peptide-based vaccine development

The development of new vaccines against pathogens is an important part of infectious disease control. In the last decade, a variety of proteins giving rise to naturally processed pathogen-derived antigenic peptides, representing B-cell and T-cell epitopes, have been characterized. Numerous candidate vaccines consisting of synthetic peptides are being designed and evaluated, with encouraging results. In this context, the application of mass spectrometry based on the isolation and identification of pathogen-derived peptides from the human leukocyte antigen (HLA) molecules is a major focus of peptide-based vaccine development. Dramatic improvements have been made in mass spectrometer performance for peptide sequencing in terms of increased sensitivity, the ability to rapidly obtain data-directed tandem mass spectra, and the accuracy of mass measurement. This review focuses on the efforts to identify T-cell epitopes for viral and microbial pathogens for directed vaccine development.

Antidepressant use in multiple sclerosis: epidemiologic study of a large community sample

Depressive symptoms and disorders among individuals with multiple sclerosis (MS) are more common when compared to other chronic illnesses and the general population, but relatively little is known about the use of antidepressant medication in this population. In this cross-sectional study of 542 community-dwelling adults with MS, we examined the prevalence of antidepressant use and employed multivariate logistic regression modeling to identify factors significantly associated with antidepressant use. Thirty-five percent of the sample reported currently using at least one antidepressant medication. Gender, marital status, insurance status, fatigue, and use of disease modifying therapies were all significantly associated with antidepressant use. Just over half of the sample endorsed a clinically significant level of depressive symptoms, and the majority of this group was not currently taking an antidepressant. Conversely, 41% of those with depressive symptoms reported taking at least one antidepressant medication. More research is needed to better understand why people with MS and depressive symptoms use or do not use antidepressant medications and to further explore the possibility of an under-treatment of depressive disorder in this population. Rigorous studies testing the feasibility, acceptability, and efficacy of currently available therapies for depression in the MS population should also be conducted. Multiple Sclerosis 2007; 13: 1046—1053. http://msj.sagepub.com

Comparing a self report questionnaire with physician assessment for determining multiple sclerosis clinical disease course: a validation study

Determining multiple sclerosis (MS) clinical course is important in research and clinical practice. However, many patients do not know their clinical course, limiting the option to use self-report in research studies including surveys. In order to address this, we developed a self-report item to be used in self-administered mailed surveys displaying graphically the courses of MS. The validity of this item was then evaluated by comparing physician-assessed disease clinical course to patient response on the self-report item on 94 of 99 consecutive patients seen in an MS specialty clinic. Kappa statistics were calculated comparing self-assessed versus physician-assessed MS clinical course for the four common MS clinical courses (κ=0.45) and for relapsing remitting versus other courses (κ=0.62) indicating substantial agreement. Subsequent administration of the item by mail to 1371 individuals with MS in Washington and Montana determined that while most individuals responded as intended to the item, persons with less than a high school education ( P=0.009) or over the age of 60 ( P = 0.002) were significantly more likely to leave the item blank. It appears that this item may be used to obtain a rough estimate of MS clinical course in research using self-report surveys where physician assessments are impractical. Multiple Sclerosis 2007; 13: 1033—1037. http://msj.sagepub.com

Residual stresses in rolling contact

The paper reports an experimental investigation into the residual strsses induced into cylndrical discs by the action of rolling-contact loads sufficiently high to cause some plastic deformation in the near-surface layers.

A general method is first described for finding both circumferential and axial components of residual stress in cylindrical bodies in circumstances where the stresses vary with the radial co-ordinate only. This method is believed to be an improvement on previous methods for separating the two components of residual stress, particularly where only specimens of restricted length are available. For example, the method could be applied to thick-walled tubes.

Measurements have been made of the residual stresses due to rolling contact, in pure rolling and in combined rolling and sliding. In all cases both components of residual stress were compressive and reached a maximum value below the surface at about the depth of the maximum Hertz shear stress. The measured residual stresses in the sub-surface region were roughly in agreement with the theoretical predictions of Merwin, Johnson, and Jefferis.

A subsidiary peak of compressive stress was found at the surface itself. Neither the surface nor the subsurface stresses were found to be greatly influenced by the presence of friction forces when sliding accompanied rolling.

Nuclear factor kappaB p65 phosphorylation in orthodontic tooth movement

Osteoclasts play a vital role in orthodontic tooth movement. Transactivation of nuclear factor kappaB (NFkappaB) by phosphorylation of the p65 component of NFkappaB at amino acid 536 (p65*(536)) plays a role in osteoclast differentiation stimulated by receptor activator of nuclear factor kappaB-ligand (RANK-L). We hypothesized that this transactivation pathway might be involved in the responses of alveolar bone cells during orthodontic tooth movement. We detected sharp increases in the levels of p65*(536) 3 and 12 hrs after the application of orthodontic stimuli in rats. In cell culture, osteoclast-like cells displayed no changes in p65*(536) in response to RANK-L, but levels rapidly increased after the cells were mechanically scraped. We conclude that p65*(536) is produced rapidly in response to orthodontic stimuli and mechanical insults, and may be important in bone remodeling associated with orthodontic tooth movement.

Antibodies to Trophoblast Antigens HLA-G, Placenta Growth Factor, and NeuroD2 Do Not Improve Detection of Circulating Trophoblast Cells in Maternal Blood

OBJECTIVES

Non-invasive prenatal diagnosis using circulating fetal trophoblast cells has been challenging due to lack of a reproducible trophoblast-specific antibody. We investigated the use of three trophoblast cell-specific antibodies, HLA-G, placenta growth factor, and neuroD2, for the isolation of trophoblast cells from the maternal circulation.

METHODS

Trophoblast cells were isolated by density centrifugation from maternal blood samples (gestational age 10-20 weeks, n = 9). All women were carrying a male fetus. Following immunocytochemical staining with the trophoblast-specific antibodies, fluorescent in situ hybridization was performed, to verify whether any stained cells were indeed fetal.

RESULTS

The HLA-G antibody had a ubiquitous staining pattern, which was not specific for trophoblast cells. Neither the placenta growth factor nor the neuroD2 antibodies were able to identify any trophoblast cells. Following fluorescent in situ hybridization, no male cells were detected on any of the slides.

CONCLUSION

The antibodies used in this study were unable to improve detection of trophoblast cells in the maternal circulation.

Fetal cells participate over time in the response to specific types of murine maternal hepatic injury

BACKGROUND

In humans, fetal microchimeric cells transferred to maternal tissues during pregnancy can adopt a hepatocyte phenotype. Our objective was to determine whether fetal cells participate in the response to specific murine post-partum hepatic injuries.

METHODS

Wild-type female mice were bred to males transgenic for the enhanced green fluorescent protein (GFP) (n = 42). Following delivery, we created models of chemical or surgical injury with carbon tetrachloride (CCl(4)) injection or by performing partial hepatectomy. Liver injury was assessed histologically. Fetal cells in maternal liver were detected and measured by real-time PCR amplification of the gfp transgene and by immunofluorescence using anti-GFP antibodies.

RESULTS

PCR results showed that in chemical but not surgical injury, fetal GFP+ cells were detectable in maternal liver and spleen and that fetal cell presence was significantly increased over time following injury (4 versus 8 weeks, P = 0.006 for liver and P = 0.0006 for spleen). In some animals, following chemical injury, GFP+ cells were detected by immunofluorescence.

CONCLUSIONS

The results of this preliminary study suggest that specific types of injury may elicit different fetal cell responses in maternal organs. There is a significant effect of time on fetal cell presence in liver and spleen. Furthermore, real-time PCR amplification is more sensitive than immunofluorescence for the detection of microchimeric fetal cells.

Regression analysis for comparing protein samples with 16O/18O stable-isotope labeled mass spectrometry

MOTIVATION

Using stable isotopes in global proteome scans, labeled molecules from one sample are pooled with unlabeled molecules from another sample and subsequently subjected to mass-spectral analysis. Stable-isotope methodologies make use of the fact that identical molecules of different stable-isotope compositions are differentiated in a mass spectrometer and are represented in a mass spectrum as distinct isotopic clusters with a known mass shift. We describe two multivariable linear regression models for (16)O/(18)O stable-isotope labeled data that jointly model pairs of resolved isotopic clusters from the same peptide and quantify the abundance present in each of the two biological samples while concurrently accounting for peptide-specific incorporation rates of the heavy isotope. The abundance measure for each peptide from the two biological samples is then used in down-stream statistical analyses, e.g. differential expression analysis. Because the multivariable regression models are able to correct for the abundance of the labeled peptide that appear as an unlabeled peptide due to the inability to exchange the natural C-terminal oxygen for the heavy isotope, they are particularly advantageous for a two-step digestion/labeling procedure. We discuss how estimates from the regression model are used to quantify the variability of the estimated abundance measures for the paired samples. Although discussed in the context of (16)O/(18)O stable-isotope labeled data, the multivariable regression models are generalizable to other stable-isotope labeled technologies.

Oscillating adhesive contacts between micron-scale tips and compliant polymers

Adhesion of micron-scale probes with model poly(dimethylsiloxane), PDMS, elastomers was studied with a depth-sensing nanoindenter under oscillatory loading conditions. For contacts between diamond indenters (radius R = 5 or 10 microm) and PDMS, force-displacement curves were highly reversible and consistent with Johnson-Kendall-Roberts (JKR) behavior. However, our experiments have revealed striking differences between the experimental measurements of tip-sample interaction stiffness and the theoretical JKR stiffness. The measured stiffness was always greater than zero, even in the reflex portion of the curve (between the maximum adhesive force and release), where the JKR stiffness is negative. This apparent paradox can be resolved by considering the effects of viscoelasticity of PDMS on an oscillating crack tip in a JKR contact. Under well described conditions determined by oscillation frequency, sample viscoelastic properties, and the Tabor parameter (with variables R, reduced elastic modulus, E*, and interfacial energy, deltagamma), an oscillating crack tip will neither advance nor recede. In that case, the contact size is fixed (like that of a flat punch) at any given point on the load-displacement cycle, and the experimentally measured stiffness is equal to the equivalent punch stiffness. For a fixed oscillation frequency, a transition between JKR and punch stiffness can be brought about by an increase in radius of the probe or a decrease in PDMS modulus. Additionally, varying the oscillation frequency for a fixed E*, R, and deltagamma also resulted in transition between JKR and punch stiffness in a predictable manner. Comparisons of experiments and theory for an oscillating viscoelastic JKR contact are presented. The storage modulus and surface energy from nanoscale JKR stiffness measurements were compared to calculated values and those measured with conventional nanoindentation and JKR force-displacement analyses.

Oscillatory loading of a viscoelastic adhesive contact

The cycle of loading and unloading of a spherically-tipped probe against an adhesive, viscoelastic plane specimen is studied by numerical integration of the relations between crack speed and apparent surface energy previously found for a linear 3-element viscoelastic solid with a Maugis-Dugdale law of force across the crack. It is found that even when the rate of loading is so slow that the loading and unloading curves almost coincide, suggesting purely elastic behaviour, the pull-off force can be appreciably greater than the elastic (JKR) value. When the normal force is modulated with a small amplitude sinusoidal variation during unloading--in order to find the contact stiffness--the contact radius barely changes, and the stiffness is close to that for a rigid flat punch instead of having the expected JKR value.

Vocational rehabilitation in multiple sclerosis (MS): a profile of clients seeking services

Although a number of innovative vocational rehabilitation (VR) demonstration projects have been completed with MS populations, there remains a lack of clarity as to a profile of these VR participants. An effort is made in this article to carefully describe the demographic and occupational characteristics of people with MS seeking vocational services at intake, as well as their self-perceived psychosocial functioning across a range of pertinent measures. The issue of "program dropouts" in VR services for people with MS is also addressed. Implications for better understanding participants with MS within the VR process and improved nuances in service delivery are then discussed.

Expression and function of HLA-DR3 and DQ8 in transgenic mice lacking functional H2-M

H2-M or HLA-DM are non-classical class II molecules encoded by the MHC and play an important role during antigen presentation. They catalyze exchange of CLIP (Class II-associated invariant chain peptide) or other low-affinity peptides bound to class II molecules for peptides capable of more efficient binding. The phenotype of mice lacking H2-M is determined by the allotype of the MHC class II molecules expressed. In general, H2-M deficiency does not affect the surface expression of mature class II molecules. The class II molecules in such cases predominantly contain CLIP in their peptide-binding groove. In some mice strains, H2-M deficiency results in defective CD4+ T-cell development accompanied by defective responses to conventional antigens and superantigens. Even though the HLA class II molecules show similar dependency for HLA-DM for presenting antigens in vitro, their interaction in vivo is not known. By using transgenic approach we show here that DQ8 and DR3 are expressed at normal levels in H2-M-deficient mice and the CD4+ T-cell development is unaltered. However, the ability of DQ8 molecules to present peptide antigens is compromised in a H2-M-deficient state. Presentation of exogenous bacterial superantigens by both DQ8 and DR3 is unaffected in H2-M-deficient mice. Unexpectedly, Staphylococcal Enterotoxin B-induced systemic IFN-gamma production was significantly higher in H2-M-deficient DQ8/DR3 transgenic mice and these mice were susceptible to SEB-induced toxic shock at doses that are non-lethal to H2-M-sufficient counterparts.

Fetal gender and aneuploidy detection using fetal cells in maternal blood: analysis of NIFTY I data. National Institute of Child Health and Development Fetal Cell Isolation Study

OBJECTIVES

The National Institute of Child Health and Human Development Fetal Cell Isolation Study (NIFTY) is a prospective, multicenter clinical project to develop non-invasive methods of prenatal diagnosis. The initial objective was to assess the utility of fetal cells in the peripheral blood of pregnant women to diagnose or screen for fetal chromosome abnormalities.

METHODS

Results of fluorescence in situ hybridization (FISH) analysis on interphase nuclei of fetal cells recovered from maternal blood were compared to metaphase karyotypes of fetal cells obtained by amniocentesis or chorionic villus sampling (CVS). After the first 5 years of the study we performed a planned analysis of the data. We report here the data from 2744 fully processed pre-procedural blood samples; 1292 samples were from women carrying singleton male fetuses.

RESULTS

Target cell recovery and fetal cell detection were better using magnetic-based separation systems (MACS) than with flow-sorting (FACS). Blinded FISH assessment of samples from women carrying singleton male fetuses found at least one cell with an X and Y signal in 41.4% of cases (95% CI: 37.4%, 45.5%). The false-positive rate of gender detection was 11.1% (95% CI: 6.1,16.1%). This was higher than expected due to the use of indirectly labeled FISH probes in one center. The detection rate of finding at least one aneuploid cell in cases of fetal aneuploidy was 74.4% (95% CI: 76.0%, 99.0%), with a false-positive rate estimated to be between 0.6% and 4.1%.

CONCLUSIONS

The sensitivity of aneuploidy detection using fetal cell analysis from maternal blood is comparable to single marker prenatal serum screening, but technological advances are needed before fetal cell analysis has clinical application as part of a multiple marker method for non-invasive prenatal screening. The limitations of the present study, i.e. multiple processing protocols, are being addressed in the ongoing study.

Microchimerism of presumed fetal origin in thyroid specimens from women: a case-control study

BACKGROUND

Some so-called autoimmune diseases in women might be alloimmune and represent a chronic graft-versus-host response attributable to transplacentally acquired fetal cells. Thyroid disease is more common in women than men, and post partum exacerbation of thyroiditis is common. Our aim was to investigate whether there is an association between fetal cell microchimerism and thyroid disease in women.

METHODS

Surgical specimens were obtained from 29 women who underwent thyroidectomy for various thyroid disorders. Control specimens were taken from clinically and histologically normal thyroids obtained at necropsy from eight women who died from unrelated conditions. Medical records and pregnancy histories were reviewed. Fluorescence in-situ hybridisation analysis was done with probes specific for X and Y chromosomes. Slides were examined with a fluorescence microscope to detect the presence of male cells-with one X and one Y signal in the nucleus-among maternal cells containing two X signals.

FINDINGS

Male cells were seen in thyroid sections from 16 patients but not in those from controls (p=0.01). Male cells (1-165 per slide) were seen individually or in clusters in all thyroid diseases and were not restricted to inflammatory thyroid diseases. In one patient with a progressively enlarging goitre, we noted fully differentiated male thyroid follicles closely attached to and indistinguishable from the rest of the thyroid.

INTERPRETATION

Our findings suggest a relation between fetal cell microchimerism and thyroid disease. Furthermore, fetal stem cells might be capable of differentiation into mature thyroid follicles in their mothers with favourable environmental and developmental factors.

Fetal and maternal progenitor cells in co-culture respond equally to erythropoietin

To explore potentially selective growth conditions for fetal cells in cultures from the blood of pregnant women, we investigated if fetal and adult erythroid progenitors with different hemoglobin expression programs are differentially responsive to erythropoietin (EPO). Co-cultures of clonogenic cells from 12-week fetal and adult peripheral blood were established, and the development of erythropoietic cells was monitored using flow cytometric profiles of correlated cellular contents of fetal and adult hemoglobin (HbF and HbA, respectively). Adult nucleated red cells were classified as F+A-, F+A+ or F-A+. All fetal cells were F+A-. The population of F+A- cells was flow-sorted and fetal cells were identified by fluorescence in situ hybridization (FISH) using chromosome-specific probes. Delayed EPO addition revealed that all types of erythroid cells entered the EPO-dependent phase with similar kinetics, beginning at about Day 4. The data suggest that fetal and adult erythroid stem/progenitor cells have the same initial maturation kinetics in culture independent of their hemoglobin chain expression program. Fetal and adult cells with different hemoglobin profiles also showed similar EPO dose-response curves, determined for different intervals during the first 2 weeks of culture. Thus, the kinetics of entry into the phase of EPO dependence, as well as the sensitivity to EPO at various stages of development, are essentially the same for erythropoietic progenitor cells derived from adult and early fetal blood, which rules out the possibility of using the timing or concentration of EPO for the selective growth of fetal cells from the blood of pregnant women.

The complex structures of arabinogalactan-proteins and the journey towards understanding function

Arabinogalactan-proteins (AGPs) are a family of complex proteoglycans found in all higher plants. Although the precise function(s) of any single AGP is unknown, they are implicated in diverse developmental roles such as differentiation, cell-cell recognition, embryogenesis and programmed cell death. DNA sequencing projects have made possible the identification of the genes encoding a large number of putative AGP protein backbones. In contrast, our understanding of how AGPs undergo extensive post-translational modification is poor and it is important to understand these processes since they are likely to be critical for AGP function. Genes believed to be responsible for post-translational modification of an AGP protein backbone, include prolyl hydroxylases, glycosyl transferases, proteases and glycosylphosphatidylinositol-anchor synthesising enzymes. Here we examine models for proteoglycan function in animals and yeast to highlight possible strategies for determining the function(s) of individual AGPs in plants.

Microchimerism in a female patient with systemic lupus erythematosus

Systemic lupus erythematosus (SLE) is a serious multisystem disease that has a striking propensity to affect women. The cause of SLE remains elusive. Fetomaternal cell trafficking, or the passage of fetal cells into the maternal circulation, is now a well-established phenomenon. In addition, fetal cells have been implicated in the development of preeclampsia and in the pathogenesis of scleroderma. We undertook this study to determine whether fetomaternal cell trafficking might also be involved in pathogenic processes in SLE. Fluorescence in situ hybridization analysis was performed using X and Y chromosome-specific probes on affected and unaffected tissue obtained at autopsy from a woman who had previously given birth to 2 males and who had died of complications of SLE. The goal of the analysis was to detect the presence of male cells of putative fetal origin. Male cells were found in every histologically abnormal tissue type that was examined, but were not found in histologically normal tissue. These data suggest that fetal cells may be associated with SLE. It is unclear whether their presence may be related to disease causation, an effect of disease progression, or unrelated to disease pathology. However, this case study is an important step toward understanding the potential relationship between fetomaternal cell trafficking and SLE pathology.

Diagnosis of trisomy 21 in fetal nucleated erythrocytes from maternal blood by use of short tandem repeat sequences

BACKGROUND

The purpose of this study was to determine whether aneuploid fetal nucleated erythrocytes (NRBCs) could be detected in maternal blood through the use of fluorescent PCR amplification with polymorphic short tandem repeat (STR) markers as an alternative or complementary method to analysis by fluorescent in situ hybridization (FISH).

METHODS

Peripheral blood samples were obtained from women who had just undergone termination of pregnancy because of fetal trisomy 21 (three cases, 47,XY,+21; four cases, 47,XX,+21). Candidate fetal cells were isolated by flow-sorting by antibodies to the gamma chain of fetal hemoglobin and Hoechst 33342. FISH analysis was performed by the use of chromosome-specific probes for X, Y, and 21. Fetal NRBCs, as defined by the presence of gamma staining, characteristic morphology, and three chromosome 21 signals, along with maternal leukocytes, defined as gamma negative and two chromosome 21 signals, were micromanipulated separately and subjected to fluorescent PCR amplification of chromosome 21 STR markers (D21S11, D21S1411, and/or D21S1412).

RESULTS

In five of seven cases analyzed, fetal NRBCs were aneuploid, as determined by the presence of triallelic or diallelic peaks of chromosome 21 sequences when compared with sequences from the maternal leukocytes.

CONCLUSIONS

Fluorescent PCR amplification of STRs can detect fetal aneuploidy and may be useful in the setting of poor hybridization efficiency with FISH analysis. These results suggest that combined fetal aneuploidy and single-gene diagnoses by the use of DNA microarrays may be feasible in the near future.

Fetal cell microchimerism in tissue from multiple sites in women with systemic sclerosis

OBJECTIVE

The realization that fetal cells pass into the maternal circulation and can survive for many years has raised the question of whether fetal microchimerism can cause subsequent disease in the mother. Available data suggest that fetal-maternal transfusion may be related to some autoimmune diseases, notably systemic sclerosis (SSc). The goal of the current work was to identify and quantify tissue-specific fetal microchimerism in women with SSc.

METHODS

We analyzed multiple tissue specimens obtained at autopsy from women with SSc as well as women who had died of causes unrelated to autoimmunity, using fluorescence in situ hybridization to detect the presence of male cells in women with sons. Tissues analyzed included adrenal gland, heart, intestine, kidney, liver, lung, lymph node, pancreas, parathyroid, skin, and spleen.

RESULTS

Male cells were observed in tissue from at least 1 site in each woman with SSc and were found most frequently in spleen sections. After spleen, male cells were observed most frequently in lymph node, lung, adrenal gland, and skin tissue. The only tissue type in which male cells were not seen in any patient was pancreatic tissue. Male cells were not observed in tissue from women who had died of causes unrelated to autoimmunity.

CONCLUSION

The results of this study suggest that fetal cells migrate from the peripheral circulation into multiple organs in women with SSc. All of the women studied had previously given birth to sons, so it is likely that these cells are of fetal origin. While the relevance of this finding to the pathogenesis of SSc remains to be elucidated, the presence of fetal cells in internal organs suggests that they could play a role in disease pathogenesis and that they may preferentially sequester in the spleen. The presence of these male cells may also be a result of disease, possibly through the migration of terminally differentiated and/or progenitor cells to areas of tissue damage.

Mitochondrial cytochrome c release is caspase-dependent and does not involve mitochondrial permeability transition in didemnin B-induced apoptosis

Permeability transition, and a subsequent drop in mitochondrial membrane potential (DeltaPsi(m)), have been suggested to be mechanisms by which cytochrome c is released from the mitochondria into the cytosol during apoptosis. Furthermore, a drop in DeltaPsi(m) has been suggested to be an obligate early step in the apoptotic pathway. Didemnin B, a branched cyclic peptolide described to have immunosuppressive, anti-tumour, and anti-viral properties, induces rapid apoptosis in a range of mammalian cell lines. Induction of apoptosis by didemnin B in cultured human pro-myeloid HL-60 cells is the fastest and most complete ever described with all cells being apoptotic after 3 h of treatment. By utilizing the system of didemnin B-induced apoptosis in HL-60 cells, and the potent inhibitors of mitochondrial permeability transition, cyclosporin A and bongkrekic acid, we show that permeability transition as determined by changes in DeltaPsi(m) and mitochondrial Ca2+ fluxing, is not a requirement for apoptosis or cytochrome c release. In this system, changes in mitochondrial membrane potential and cytochrome c release are shown to be dependent on caspase activation, and to occur concurrently with the release of caspase-9 from mitochondria, genomic DNA fragmentation and apoptotic body formation.

The role of mass spectrometry in vaccine development

For the most part, vaccine development to date has been empiric. While sometimes successful, such a strategy is 'hit or miss', and fails to advance the basic science of vaccine development. Preferable would be tools that allow for a more directed development of vaccines at either the population or sub-population level. Characteristics of useful tools in vaccine development should include the ability to identify and characterize the spectrum of antigenic peptides presented by MHC molecules to which the immune system responds by the development of protective immune responses. In addition, because the explosion in human genomics allows the ability to understand MHC haplotypes at the population level, as well as an enhanced understanding of MHC binding motifs, new tools might further allow for an understanding of which vaccine antigens are capable of being bound and presented to the immune system by MHC molecules. New mass spectrometry technology fulfils these criteria, and may well lead to a revolution in the design of new vaccines. This paper will review the basics of mass spectrometry techniques as applied to the identification and characterization of vaccine peptide antigens, and discusses how these tools can be applied to vaccine development.

Determination of in vivo adducts of disulfiram with mitochondrial aldehyde dehydrogenase

Extensive use for disulfiram (DSF) has been found in the aversion therapy treatment of recovering alcoholics. Although it is known to irreversibly inhibit hepatic aldehyde dehydrogenase (ALDH), the specific mechanism of in vivo inhibition of the enzyme by the drug has not been determined yet. We have demonstrated in this report a novel, but simple and rapid method for structurally characterizing in vivo derived protein-drug adducts by linking on-line sample processing to HPLC-electrospray ionization mass spectrometry (HPLC-MS) and HPLC-tandem mass spectrometry (HPLC-MS/MS). Employing this approach, rats were administered DSF, and their liver mitochondria were isolated and solubilized. Both native and in vivo DSF-treated mitochondrial ALDH (mALDH) were purified in one step with an affinity cartridge. The in vivo DSF-treated mALDH showed 77% inhibition in enzyme activity as compared with that of the control. Subsequently, the control and DSF-inhibited mALDH were both subjected to HPLC-MS analyses. We were able to detect two adducts on DSF-inhibited mALDH, as indicated by the mass increases of approximately 71 and approximately 100 Da. To unequivocally determine the site and structure of these adducts, on-line pepsin digestion-HPLC-MS and HPLC-MS/MS were performed. We observed two new peptides at MH(+) = 973.7 and MH(+) = 1001.8 in the pepsin digestion of DSF-inhibited enzyme. These two peptides were subsequently subjected to HPLC-MS/MS for sequence determination. Both peptides possessed the sequence FNQGQC(301)C(302)C(303), derived from the enzyme active site region, and were modified at Cys(302) by N-ethylcarbamoyl (+71 Da) and N-diethylcarbamoyl (+99 Da) adducts. These findings indicated that N-dealkylation may be an important step in DSF metabolism, and that the inhibition of ALDH occurred by carbamoylation caused by one of the DSF metabolites, most likely S-methyl-N,N-diethylthiocarbamoyl sulfoxide (MeDTC-SO). Finally, there was no evidence of the presence of an intramolecule disulfide bridge modification on the peptide FNQGQCCC.

Effect of enzyme inhibitors on protein quaternary structure determined by on-line size exclusion chromatography-microelectrospray ionization mass spectrometry

Aldehyde dehydrogenases (ALDH) are a family of enzymes primarily involved in the oxidation of various aldehydes. Most ALDH enzymes derived from mammalian sources have been shown to exist as homotetramers, consisting of four identical subunits of approximately 54 kDa. The presence of the homotetramer appears to be necessary for enzyme activity. In this study, recombinant rat liver mitochondrial ALDH (rmALDH) was inhibited in vitro with four different inhibitors, namely, disulfiram (MW, 296.5), prunetin (MW, 284.3), benomyl (MW, 290.3), and N-tosyl-L-phenylalanine chloromethyl ketone (TPCK) (MW, 351.8). Subsequently, inhibited rmALDH was analyzed by a novel approach of on-line size exclusion chromatography-microelectrospray ionization-mass spectrometry (SEC-muESI-MS) to examine the noncovalent quaternary structural stability of the inhibited enzyme. Analysis of native rmALDH by SEC-muESI-MS revealed predominantly the homotetramer (Mr = approximately 217,457 Da, +/- 0.01%) with some in-source, skimmer-induced dissociation to afford monomer (Mr = approximately 54,360 Da, +/- 0.01%). Both disulfiram and prunetin inhibited rmALDH by >70% and >90%, respectively, but did not disrupt the quaternary structure of rmALDH. Furthermore, there was no detectable change within experimental error (+/- 0.01%) of the disulfiram or the prunetin homotetramers (Mr = approximately 217,448 Da and Mr = approximately 217,446 Da). This may possibly indicate that inhibition occurred via formation of intramolecular disulfide bond at the enzyme active site, or weak affinity noncovalent binding. In contrast, benomyl-inhibited rmALDH homotetramer (>90% inhibition) exhibited a Mr = approximately 217,650 Da (+/- 0.01%) corresponding to two butylcarbamoyl adducts on two of the four enzyme subunits. The skimmer-induced monomer afforded a mixture of unmodified rmALDH (Mr = approximately 54,365 Da, +/- 0.01%) and butylcarbamoylated enzyme (Mr = approximately 54,459 Da, +/- 0.01%). Finally, TPCK (>90% inhibition) modified all four subunits of rmALDH to give Mr = approximately 218,646 Da (+/- 0.01%). In all four cases while significant enzyme inhibition occurred, no destabilization of the quaternary complex was detected.