Genome-wide Association Study for AKI

Key Points

Two genetic variants in the DISP1-TLR5 gene locus were associated with risk of AKI. DISP1 and TLR5 were differentially regulated in kidney biopsy tissue from patients with AKI compared with no AKI.

Background

Although common genetic risks for CKD are well established, genetic factors influencing risk for AKI in hospitalized patients are poorly understood.

Methods

We conducted a genome-wide association study in 1369 participants in the Assessment, Serial Evaluation, and Subsequent Sequelae of AKI Study; a multiethnic population of hospitalized participants with and without AKI matched on demographics, comorbidities, and kidney function before hospitalization. We then completed functional annotation of top-performing variants for AKI using single-cell RNA sequencing data from kidney biopsies in 12 patients with AKI and 18 healthy living donors from the Kidney Precision Medicine Project.

Results

No genome-wide significant associations with AKI risk were found in Assessment, Serial Evaluation, and Subsequent Sequelae of AKI (P < 5×10 −8 ). The top two variants with the strongest association with AKI mapped to the dispatched resistance-nodulation-division (RND) transporter family member 1 (DISP1) gene and toll-like receptor 5 (TLR5) gene locus, rs17538288 (odds ratio, 1.55; 95% confidence interval, 1.32 to 182; P = 9.47×10 −8 ) and rs7546189 (odds ratio, 1.53; 95% confidence interval, 1.30 to 1.81; P = 4.60×10 −7 ). In comparison with kidney tissue from healthy living donors, kidney biopsies in patients with AKI showed differential DISP1 expression in proximal tubular epithelial cells (adjusted P = 3.9× 10−2) and thick ascending limb of the loop of Henle (adjusted P = 8.7× 10−3) and differential TLR5 gene expression in thick ascending limb of the loop of Henle (adjusted P = 4.9× 10−30).

Conclusions

AKI is a heterogeneous clinical syndrome with various underlying risk factors, etiologies, and pathophysiology that may limit the identification of genetic variants. Although no variants reached genome-wide significance, we report two variants in the intergenic region between DISP1 and TLR5 , suggesting this region as a novel risk for AKI susceptibility.

Genome-Wide Association Study Identifies Two Novel Loci Associated with Female Stress and Urgency Urinary Incontinence

PURPOSE

Genome-wide association studies have not identified replicable genetic risk loci for stress or urgency urinary incontinence.

MATERIALS AND METHODS

We carried out a discovery stage, case control, genome-wide association study in 3 independent discovery cohorts of European women (8,979) for stress incontinence, urgency incontinence, and any incontinence phenotypes. We conducted replication in 6 additional studies of European ancestry (4,069). We collected bladder biopsies from women with incontinence (50) to further investigate bladder expression of implicated genes and pathways and used symptom questionnaires for phenotyping. We conducted meta-analyses using inverse variance fixed effects models and whole transcriptome analyses using Affymetrix® arrays with replication with TaqMan® polymerase chain reaction.

RESULTS

In the discovery stage, we identified 16 single nucleotide polymorphisms genotyped or imputed at 5 loci that reached genome-wide significance (p <5×10-8). In replication, rs138724718 on chromosome 2 near the macrophage receptor with collagenous structure (MARCO) gene (replication p=0.003) was associated with stress incontinence. In addition, rs34998271 on chromosome 6 near the endothelin 1 (EDN1) gene (replication p=0.0008) was associated with urgency incontinence. In combined meta-analyses of discovery and replication cohorts, associations with genome-wide significance for these 2 single nucleotide polymorphisms were confirmed. Transcriptomics analyses showed differential expression of 7 of 19 genes in the endothelin pathway between stress and urgency incontinence (p <0.0001).

CONCLUSIONS

We uncovered 2 new risk loci near the genes endothelin 1 (EDN1), associated with urgency incontinence, and macrophage receptor with collagenous structure (MARCO), associated with stress incontinence. These loci are biologically plausible given their roles in smooth muscle contraction and innate host defense, respectively.

Loci identified by a genome-wide association study of carotid artery stenosis in the eMERGE network

Carotid artery atherosclerotic disease (CAAD) is a risk factor for stroke. We used a genome-wide association (GWAS) approach to discover genetic variants associated with CAAD in participants in the electronic Medical Records and Genomics (eMERGE) Network. We identified adult CAAD cases with unilateral or bilateral carotid artery stenosis and controls without evidence of stenosis from electronic health records at eight eMERGE sites. We performed GWAS with a model adjusting for age, sex, study site, and genetic principal components of ancestry. In eMERGE we found 1793 CAAD cases and 17,958 controls. Two loci reached genome-wide significance, on chr6 in LPA (rs10455872, odds ratio [OR] (95% confidence interval [CI]) = 1.50 (1.30-1.73), p = 2.1 × 10^-8 ) and on chr7, an intergenic single nucleotide variant (SNV; rs6952610, OR (95% CI) = 1.25 (1.16-1.36), p = 4.3 × 10^-8 ). The chr7 association remained significant in the presence of the LPA SNV as a covariate. The LPA SNV was also associated with coronary heart disease (CHD; 4199 cases and 11,679 controls) in this study (OR (95% CI) = 1.27 (1.13-1.43), p = 5 × 10^-5 ) but the chr7 SNV was not (OR (95% CI) = 1.03 (0.97-1.09), p = .37). Both variants replicated in UK Biobank. Elevated lipoprotein(a) concentrations ([Lp(a)]) and LPA variants associated with elevated [Lp(a)] have previously been associated with CAAD and CHD, including rs10455872. With electronic health record phenotypes in eMERGE and UKB, we replicated a previously known association and identified a novel locus associated with CAAD.

Risk factors for orgasmic and concomitant erectile dysfunction in men with type 1 diabetes: a cross-sectional study

In this study, we sought to determine the burden and characteristics of orgasmic dysfunction (OD) and concomitant erectile dysfunction (ED) in men with type 1 diabetes (T1D) enrolled in the Epidemiology of Diabetes Interventions and Complications (EDIC) study. In 2010, we assessed orgasmic and erectile function using the International Index of Erectile Function (IIEF). Sociodemographic, clinical, and diabetes characteristics were compared by OD status (OD only, OD and ED, no ED or OD). Age-adjusted associations between risk factors and OD status were examined. OD and ED information was available from 563 men. Eighty-three men (14.7%) reported OD of whom 21 reported OD only and 62 reported OD and ED. Age-adjusted odds ratios demonstrated that men who reported OD only had higher odds of depression, low sexual desire, and decreased alcohol use compared with men reporting no dysfunction. Men with OD concomitant with ED had greater odds of elevated hemoglobin A1C, peripheral and autonomic neuropathy, and nephropathy. Men reporting both dysfunctions were also more likely to report smoking, lower urinary tract symptoms, and had greater odds of androgen deficiency than men with no sexual dysfunction. Men with longstanding T1D suffer from an increased burden of OD. Psychogenic factors predominate in men reporting OD only while men who present with concomitant ED report increased burden of diabetes severity, characteristics previously observed with incident ED. ED may be the central impediment to sexual function in men with OD and ED. Longitudinal studies to characterize OD and ED experience over time are warranted.

Probing the Virtual Proteome to Identify Novel Disease Biomarkers

BACKGROUND

Proteomic approaches allow measurement of thousands of proteins in a single specimen, which can accelerate biomarker discovery. However, applying these technologies to massive biobanks is not currently feasible because of the practical barriers and costs of implementing such assays at scale. To overcome these challenges, we used a "virtual proteomic" approach, linking genetically predicted protein levels to clinical diagnoses in >40 000 individuals.

METHODS

We used genome-wide association data from the Framingham Heart Study (n=759) to construct genetic predictors for 1129 plasma protein levels. We validated the genetic predictors for 268 proteins and used them to compute predicted protein levels in 41 288 genotyped individuals in the Electronic Medical Records and Genomics (eMERGE) cohort. We tested associations for each predicted protein with 1128 clinical phenotypes. Lead associations were validated with directly measured protein levels and either low-density lipoprotein cholesterol or subclinical atherosclerosis in the MDCS (Malmö Diet and Cancer Study; n=651).

RESULTS

In the virtual proteomic analysis in eMERGE, 55 proteins were associated with 89 distinct diagnoses at a false discovery rate q<0.1. Among these, 13 associations involved lipid (n=7) or atherosclerosis (n=6) phenotypes. We tested each association for validation in MDCS using directly measured protein levels. At Bonferroni-adjusted significance thresholds, levels of apolipoprotein E isoforms were associated with hyperlipidemia, and circulating C-type lectin domain family 1 member B and platelet-derived growth factor receptor-β predicted subclinical atherosclerosis. Odds ratios for carotid atherosclerosis were 1.31 (95% CI, 1.08-1.58; P=0.006) per 1-SD increment in C-type lectin domain family 1 member B and 0.79 (0.66-0.94; P=0.008) per 1-SD increment in platelet-derived growth factor receptor-β.

CONCLUSIONS

We demonstrate a biomarker discovery paradigm to identify candidate biomarkers of cardiovascular and other diseases.

Genome-wide meta-analysis of 158,000 individuals of European ancestry identifies three loci associated with chronic back pain

Back pain is the #1 cause of years lived with disability worldwide, yet surprisingly little is known regarding the biology underlying this symptom. We conducted a genome-wide association study (GWAS) meta-analysis of chronic back pain (CBP). Adults of European ancestry were included from 15 cohorts in the Cohorts for Heart and Aging Research in Genomic Epidemiology (CHARGE) consortium, and from the UK Biobank interim data release. CBP cases were defined as those reporting back pain present for ≥3-6 months; non-cases were included as comparisons ("controls"). Each cohort conducted genotyping using commercially available arrays followed by imputation. GWAS used logistic regression models with additive genetic effects, adjusting for age, sex, study-specific covariates, and population substructure. The threshold for genome-wide significance in the fixed-effect inverse-variance weighted meta-analysis was p<5×10(-8). Suggestive (p<5×10(-7)) and genome-wide significant (p<5×10(-8)) variants were carried forward for replication or further investigation in the remaining UK Biobank participants not included in the discovery sample. The discovery sample comprised 158,025 individuals, including 29,531 CBP cases. A genome-wide significant association was found for the intronic variant rs12310519 in SOX5 (OR 1.08, p = 7.2×10(-10)). This was subsequently replicated in 283,752 UK Biobank participants not included in the discovery sample, including 50,915 cases (OR 1.06, p = 5.3×10(-11)), and exceeded genome-wide significance in joint meta-analysis (OR 1.07, p = 4.5×10(-19)). We found suggestive associations at three other loci in the discovery sample, two of which exceeded genome-wide significance in joint meta-analysis: an intergenic variant, rs7833174, located between CCDC26 and GSDMC (OR 1.05, p = 4.4×10(-13)), and an intronic variant, rs4384683, in DCC (OR 0.97, p = 2.4×10(-10)). In this first reported meta-analysis of GWAS for CBP, we identified and replicated a genetic locus associated with CBP (SOX5). We also identified 2 other loci that reached genome-wide significance in a 2-stage joint meta-analysis (CCDC26/GSDMC and DCC).

Longitudinal Patterns of Occurrence and Remission of Erectile Dysfunction in Men With Type 1 Diabetes

BACKGROUND

Men with diabetes are at greater risk of erectile dysfunction (ED).

AIM

To describe the natural history of ED in men with type 1 diabetes.

METHODS

We examined up to 30 years of prospectively collected annual ED status and demographic and clinical variables from 600 male participants in the Diabetes Control and Complications Trial (DCCT; 1983-1993) and its follow-up study, the Epidemiology of Diabetes Interventions and Complications (1994-present; data in this study are through 2012).

OUTCOMES

Yes vs no response to whether the participant had experienced impotence in the past year and whether he had used ED medication.

RESULTS

Sixty-one percent of men reported ED at least once during the study. For some men, the initial report of ED was permanent. For others, potency returned and was lost multiple times. Visual display of the data showed four longitudinal ED phenotypes: never (38.7%), isolated (6.7%), intermittent (41.8%), and persistent (12.8%). Men who never reported ED or in only 1 isolated year were younger, had lower body mass index, and better glycemic control than men in the intermittent and persistent groups at DCCT baseline. In a multivariable logistic model comparing men at their first year reporting ED, men who were older had lower odds of remission and men who were in the conventional DCCT treatment group had higher odds of remission.

CLINICAL TRANSLATION

If validated in other cohorts, such findings could be used to guide individualized interventions for patients with ED.

STRENGTHS AND LIMITATIONS

This is the first examination of ED with repeated measures at an annual resolution, with up to 30 years of responses for each participant. However, the yes vs no response is a limitation because the real phenotype is not binary and the question can be interpreted differently depending on the participant.

CONCLUSIONS

Age, glycemic control, and BMI were important longitudinal predictors of ED. We have described a more complex ED phenotype, with variation in remission patterns, which could offer insight into different mechanisms or opportunities for intervention. If validated in other cohorts, such findings could be used to establish more accurate prognostication of outcomes for patients with ED to guide individualized interventions. Palmer MR, Holt SK, Sarma AV, et al. Longitudinal Patterns of Occurrence and Remission of Erectile Dysfunction in Men With Type 1 Diabetes. J Sex Med 2017;14:1187-1194.

Mass spectrometry and next-generation sequencing reveal an abundant and rapidly evolving abalone sperm protein

Abalone, a broadcast spawning marine mollusk, is an important model for molecular interactions and positive selection in fertilization, but the focus has previously been on only two sperm proteins, lysin and sp18. We used genomic and proteomic techniques to bring new insights to this model by characterizing the testis transcriptome and sperm proteome of the Red abalone Haliotis rufescens. One pair of homologous, testis-specific proteins contains a secretion signal and is small, abundant, and associated with the acrosome. Comparative analysis revealed that homologs are extremely divergent between species, and show strong evidence for positive selection. The acrosomal localization and rapid evolution of these proteins indicates that they play an important role in fertilization, and could be involved in the species-specificity of sperm-egg interactions in abalone. Our genomic and proteomic characterization of abalone fertilization resulted in the identification of interesting, novel peptides that have eluded detection in this important model system for 20 years.

Adaptation of an osmotically pumped continuous in situ water sampler for application in riverine environments

We present the design of an osmotic water sampler that is adapted to and validated in freshwater. The sample is drawn into and stored in a continuous narrow bore tube. This geometry and slow pump rate (which is temperature dependent: 0.8 mL/d at 4 °C to 2.0 mL/d at 28 °C) minimizes sample dispersion. We have implemented in situ time-stamping which enables accurate study of pump rates and sample time defining procedures in field deployments and comparison with laboratory measurements. Temperature variations are common in rivers, and without an accurate time-stamping, or other defining procedure, time of sampling is ambiguous. The sampler was deployed for one month in a river, and its performance was evaluated by comparison with manually collected samples. Samples were analyzed for major ions using Ion Chromatography and collision reaction Inductively Couple Mass Spectrometry. Despite the differences of the two sampling methods (osmotic sampler averages, while manual samples provide snapshots), the two data sets show good agreement (average R(2) ≈ 0.7), indicating the reliability of the sampler and at the same time highlighting the advantages of high frequency sampling in dynamic environments.

Identifying migrations in marine fishes through stable-isotope analysis

The isotopic composition of many elements varies across both land and ocean surfaces in a predictable fashion. These stable-isotope ratios are transferred into animal tissues, potentially providing a powerful natural geospatial tag. To date, most studies using stable isotopes as geolocators in marine settings have focussed on mammals and seabirds conducting large ocean-basin scale migrations. An increasing understanding of isotopic variation in the marine environment, and improved sampling and analytical techniques, however, means that stable isotopes now hold genuine promise as a natural geolocation tag in marine fishes. Here, the theoretical background underpinning the use of stable isotopes of C, N and O in otolith, scale and muscle tissues as geolocation tools in the marine environment is reviewed, and examples of their applications are provided.

Nitrogen photoreduction on desert sands under sterile conditions

Sands from various geographic locations reduce N(2) from the air to NH(3) and traces of N(2)H(4) on exposure to sunlight. This N(2) photofixation occurs under sterile conditions on the surface of finely dispersed titanium minerals such as rutile, utilizing reducing equivalents generated through the photolysis of chemisorbed H(2)O. Abiological N(2) photofixation is suggested to be part of the nitrogen cycle in arid and semiarid regions. It is estimated that about 10 x 10(5) tons of N(2) is photoreduced on the total surface of the earth's deserts per year.

Towards the development of a fossil bone geochemical standard: An inter-laboratory study

Ten international laboratories participated in an inter-laboratory comparison of a fossil bone composite with the objective of producing a matrix and structure-matched reference material for studies of the bio-mineralization of ancient fossil bone. We report the major and trace element compositions of the fossil bone composite, using in-situ method as well as various wet chemical digestion techniques. For major element concentrations, the intra-laboratory analytical precision (%RSD(r)) ranges from 7 to 18%, with higher percentages for Ti and K. The %RSD(r) are smaller than the inter-laboratory analytical precision (%RSD(R); <15-30%). Trace element concentrations vary by approximately 5 orders of magnitude (0.1 mg kg(-1) for Th to 10,000 mg kg(-1) for Ba). The intra-laboratory analytical precision %RSD(r) varies between 8 and 45%. The reproducibility values (%RSD(R)) range from 13 to <50%, although extreme value >100% was found for the high field strength elements (Hf, Th, Zr, Nb). The rare earth element (REE) concentrations, which vary over 3 orders of magnitude, have %RSD(r) and %RSD(R) values at 8-15% and 20-32%, respectively. However, the REE patterns (which are very important for paleo-environmental, taphonomic and paleo-oceanographic analyses) are much more consistent. These data suggest that the complex and unpredictable nature of the mineralogical and chemical composition of fossil bone makes it difficult to set-up and calibrate analytical instruments using conventional standards, and may result in non-spectral matrix effects. We propose an analytical protocol that can be employed in future inter-laboratory studies to produce a certified fossil bone geochemical standard.

Imaging of cerebrospinal fluid space and movement of hydrocephalus mice using near infrared fluorescence

We have studied optical imaging of mice cerebrospinal fluid (CSF) space and flow using near infrared (NIR) fluorescence. We applied our method to image CSF space and flow in a mice hydrocephalus model. Hydrocephalus was induced in mice with intracranial injections of transforming growth factor. Hydrocephalic and control mice were imaged using our NIR fluorescence imaging system. Hydrocephalic mice showed diminished intracranial CSF flow. Our system is sufficient to show altered CSF flow in a mouse hydrocephalus model. Optical imaging using near infrared is an effective modality to image CSF space and movement.

Preliminary treatment planning and dosimetry for a clinical trial of neutron capture therapy using a fission converter epithermal neutron beam

A Phase I/II clinical trial of neutron capture therapy (NCT) was conducted at Harvard-MIT using a fission converter epithermal neutron beam. This epithermal neutron beam has nearly ideal performance characteristics (high intensity and purity) and is well-suited for clinical use. Six glioblastoma multiforme (GBM) patients were treated with NCT by infusion of the tumor-selective amino acid boronophenylalanine-fructose (BPA-F) at a dose of 14.0 g/m(2) body surface area over 90 min followed by irradiation with epithermal neutrons. Treatments were planned using NCTPlan and an accelerated version of the Monte Carlo radiation transport code MCNP 4B. Treatments were delivered in two fractions with two or three fields. Field order was reversed between fractions to equalize the average blood boron concentration between fields. The initial dose in the dose escalation study was 7.0 RBEGy, prescribed as the mean dose to the whole brain volume. This prescription dose was increased by 10% to 7.7 RBEGy in the second cohort of patients. A pharmacokinetic model was used to predict the blood boron concentration for determination of the required beam monitor units with good accuracy; differences between prescribed and delivered doses were 1.5% or less. Estimates of average tumor doses ranged from 33.7 to 83.4 RBEGy (median 57.8 RBEGy), a substantial improvement over our previous trial where the median value of the average tumor dose was 25.8 RBEGy.

Development and application of an unconstrained technique for patient positioning in fixed radiation beams

A flexible technique for positioning patients in fixed orientation radiation fields such as those used in neutron capture therapy (NCT) has been developed. The positioning technique employs reference points marked on the patient in combination with a 3D digitizer to determine the beam entry point and a template fitted to the patient's head is used to determine the proper beam orientation. A coordinate transformation between the CT image data and reference points on the patient determined by a least squares algorithm based on singular value decomposition is used to map the beam entry point from the planning system onto the patient. The technique was validated in a phantom study where the mean error in entry point placement was 1.3 mm. Five glioblastoma multiforme patients have been treated with NCT using this positioning technique.

Variable fitness effects of Wolbachia infection in Drosophila melanogaster

Maternally inherited Wolbachia bacteria are extremely widespread among insects and their presence is usually associated with parasitic modifications of host fitness. Wolbachia pipientis infects Drosophila melanogaster populations from all continents, but their persistence in this species occurs despite any strong parasitic effects. Here, we have investigated the symbiosis between Wolbachia and D. melanogaster and found that Wolbachia infection can have significant survival and fecundity effects. Relative to uninfected flies, infected females from three fly strains showed enhanced survival or fecundity associated with Wolbachia infection, one strain showed both and one strain responded positively to Wolbachia removal. We found no difference in egg hatch rates (cytoplasmic incompatibility) for crosses between infected males and uninfected females, although there were fecundity differences. Females from this cross consistently produced fewer eggs than infected females and these fecundity differences could promote the spread of infection just like cytoplasmic incompatibility. More surprising, we found that infected females often had the greatest fecundity when mated to uninfected males. This could also promote the spread of Wolbachia infection, though here the fitness benefits would also help to spread infection when Wolbachia are rare. We suggest that variable fitness effects, in both sexes, and which interact strongly with the genetic background of the host, could increase cytoplasmic drive rates in some genotypes and help explain the widespread persistence of Wolbachia bacteria in D. melanogaster populations. These interactions may further explain why many D. melanogaster populations are polymorphic for Wolbachia infection. We discuss our results in the context of host-symbiont co-evolution.

A 23,000-year record of surface water pH and PCO2 in the western equatorial Pacific Ocean

The oceans play a major role in defining atmospheric carbon dioxide (CO2) levels, and although the geographical distribution of CO2 uptake and release in the modern ocean is understood, little is known about past distributions. Boron isotope studies of planktonic foraminifera from the western equatorial Pacific show that this area was a strong source of CO2 to the atmosphere between approximately 13,800 and 15,600 years ago. This observation is most compatible with increased frequency of La Niña conditions during this interval. Hence, increased upwelling in the eastern equatorial Pacific may have played an important role in the rise in atmospheric CO2 during the last deglaciation.

Pharamacokinetic modeling for boronophenylalanine-fructose mediated neutron capture therapy: 10B concentration predictions and dosimetric consequences

A two-compartment open model has been developed for predicting 10B concentrations in blood following intravenous infusion of the L-p-boronophenylalanine-fructose complex in humans and derived from pharmacokinetic studies of 24 patients in Phase I clinical trials of boron neutron capture therapy. The 10B concentration profile in blood exhibits a characteristic rise during the infusion to a peak of approximately 32 microg/g (for infusion of 350 mg/kg over 90 min) followed by a biexponential disposition profile with harmonic mean half-lives of 0.32 +/- 0.08 and 8.2 +/- 2.7 h, most likely due to redistribution and primarily renal elimination, respectively. The mean model rate constants k12, k21, and k10 are (mean +/- SD) 0.0227 +/- 0.0064 min(-1), 0.0099 +/- 0.0027 min(-1), 0.0052 +/- 0.0016 min(-1), respectively, and the central compartment volume of distribution V1 is 0.235 +/- 0.042 L/kg. In anticipation of the initiation of clinical trials using an intense neutron beam with concomitantly short irradiations, the ability of this model to predict, in advance, the average blood 10B concentration during brief irradiations was simulated in a retrospective analysis of the pharmacokinetic data from these patients. The prediction error for blood boron concentration and its effect on simulated dose delivered for each irradiation field are reported for three different prediction strategies. In this simulation, error in delivered dose (or, equivalently, neutron fluence) for a given single irradiation field resulting from error in predicted blood 10B concentration was limited to less than 10%. In practice, lower dose errors can be achieved by delivering each field in two fractions (on two separate days) and by adjusting the second fraction's dose to offset error in the first.

A theoretical model for the microdosimetry of discontinuous distributions of heavy particle tracks

A novel approach to solving microdosimetry problems using conditional probabilities and geometric concepts has been developed. This approach is valid for cases where a convex site is immersed in uniform or discontinuous distributions of heavy charged particle tracks and assumes no restrictions in site geometry or the kind of randomness. These conditions are relevant to the study of microdosimetry in applications such as neutron capture therapy (NCT), irradiation experiments using heavy ion particle beams, environmental radon, or occupational exposure to radioactive materials. Expressions applicable to the case of surface-distributed sources of tracks are presented that may represent situations such as NCT, where boron compounds are bound to the membranes of cellular nuclei. Microdosimetric spectra, specific energy averages, and mean number of 10B capture reactions for cell inactivation are calculated, showing their dependence on 10B localisation.

A theoretical model for event statistics in microdosimetry. I: Uniform distribution of heavy ion tracks

In this work we describe a novel approach to solving microdosimetry problems using conditional probabilities and geometric concepts. The intersection of a convex site with a field of randomly oriented straight track segments is formulated in terms of the relative overlap between the chord associated with the action line of the track and the track itself. This results in a general formulation that predicts the contribution of crossers, stoppers, starters, and insiders in terms of two separate functions: the chord length distribution (characteristic of the site geometry and the type of randomness) and an independent set of conditional probabilities. A Monte Carlo code was written in order to validate the proposed approach. The code can represent the intersection between an isotropic field of charged particle tracks and a general ellipsoid of unrestricted geometry. This code was used to calculate the event distribution for a sphere as well as the expected mean value and variance of the track length distribution and to compare these against the deterministic calculations. The observed agreement was shown to be very good, within the precision of the Monte Carlo approach. The formulation is used to calculate the event frequency, lineal energy, and frequency mean specific energy for several monoenergetic and isotropic proton fields in a spherical site, as a function of the site diameter, proton energy, and the event type.

A theoretical model for event statistics in microdosimetry. II: Nonuniform distribution of heavy ion tracks

A microdosimetry model, described in Part I, applies to the case of a convex site immersed in a uniform distribution of heavy particle tracks, and assumes no restrictions in site geometry or the kind of randomness. In Part II, this model is extended to include nonuniform distributions of particle tracks. This situation is relevant to the study of microdosimetry, for example, in boron neutron capture, in irradiation experiments using heavy ion particle beams, where the sources of particle tracks are external to the cell, or in irradiation from internally incorporated particle-emitting radionuclides, such as environmental radon or occupational exposure to radioactive materials. The formalism developed permits the calculation of statistical properties, track length distributions, and microdosimetric spectra for convex sites where the "inner" and "outer" concentrations of sources may be different, or for tracks originating on the surface of a convex site. Expressions applicable to the case of surface-distributed sources of tracks are presented that may represent situations such as boron compounds bound to the membrane of a cellular nucleus in boron neutron capture. A series of Monte Carlo calculations and analytical solutions, illustrating the case of spherical site geometry, are presented and compared. Finally, microdosimetric spectra and specific energy averages are calculated for alpha and lithium particles originating from thermal neutron capture in 10B, showing their dependence on 10B localization (extra-site, uniform, intra-site, or surface-distributed).

Biological dosimetry for epithermal neutron beams

The radiobiological effectiveness of an epithermal neutron beam is described using cell survival as the end point. The M67 epithermal neutron beam at the Nuclear Reactor Laboratory, Massachusetts Institute of Technology, that was used for clinical trials of boron neutron capture therapy was used to irradiate Chinese hamster ovary cells at seven depths in a water-filled phantom that simulated healthy tissue. No boron was added to the samples. Therefore, this experiment evaluates the biological effectiveness of the neutron and photon components, which comprise 80-95% of the dose to healthy tissue. Cell survival was dependent upon the depth in the phantom, as a result of moderation and attenuation of the epithermal neutron beam components by the overlying water. The results were compared with 250 kVp X irradiations to determine relative biological effectiveness values. Cell survival as a function of the dose delivered was lowest at the most shallow depth of 0.5 cm, and increased at depths of 1.5, 3, 4, 5.6, 6.6 and 8.1 cm. The gradual increase in cell survival with increasing depth in the phantom is due to the exponential drop of the fast-neutron intensity of the beam. These results are applicable to clinical boron neutron capture therapy Phase I/II trials in which healthy tissue toxicity was an end point.

A pharmacokinetic model for the concentration of 10B in blood after boronophenylalanine-fructose administration in humans

An open two-compartment model has been developed for predicting (10)B concentrations in blood after intravenous infusion of the l-p-boronophenylalanine-fructose complex (BPA-F) in humans and derived from studies of pharmacokinetics in 24 patients in the Harvard-MIT Phase I clinical trials of BNCT. The (10)B concentration profile in blood exhibits a characteristic rise during the infusion to a peak of approximately 32 microg/g (for infusion of 350 mg/kg over 90 min) followed by a biphasic exponential clearance profile with half-lives of 0.34 +/- 0.12 and 9.0 +/- 2.7 h, due to redistribution and primarily renal elimination, respectively. The model rate constants k(1), k(2) and k(3) are 0.0227 +/- 0.0064, 0.0099 +/- 0.0027 and 0.0052 +/- 0.0016 min(-1), respectively, and the central compartment volume of distribution, V(1), is 0.235 +/- 0.042 kg/kg. The validity of this model was demonstrated by successfully predicting the average pharmacokinetic response for a cohort of patients who were administered BPA-F using an infusion schedule different from those used to derive the parameters of the model. Furthermore, the mean parameters of the model do not differ for cohorts of patients infused using different schedules.

Intranigral transplantation of solid tissue ventral mesencephalon or striatal grafts induces behavioral recovery in 6-OHDA-lesioned rats

Parkinson's disease (PD) is characterized by a degeneration of the dopamine (DA) pathway from the substantia nigra (SN) to the basal forebrain. Prior studies in unilateral 6-hydroxydopamine (6-OHDA)-lesioned rats have primarily concentrated on the implantation of fetal ventral mesencephalon (VM) into the striatum in attempts to restore DA function in the target. We implanted solid blocks of fetal VM or fetal striatal tissue into the SN to investigate whether intra-nigral grafts would restore motor function in unilaterally 6-OHDA-lesioned rats. Intra-nigral fetal striatal and VM grafts elicited a significant and long-lasting reduction in apomorphine-induced rotational behavior. Lesioned animals with ectopic grafts or sham surgery as well as animals that received intra-nigral grafts of fetal cerebellar cortex showed no recovery of motor symmetry. Subsequent immunohistochemical studies demonstrated that VM grafts, but not cerebellar grafted tissue expressed tyrosine hydroxylase (TH)-positive cell bodies and were associated with the innervation by TH-positive fibers into the lesioned SN as well as adjacent brain areas. Striatal grafts were also associated with the expression of TH-positive cell bodies and fibers extending into the lesioned SN and an induction of TH-immunolabeling in endogenous SN cell bodies. This finding suggests that trophic influences of transplanted fetal striatal tissue can stimulate the re-expression of dopaminergic phenotype in SN neurons following a 6-OHDA lesion. Our data support the hypothesis that a dopaminergic re-innervation of the SN and surrounding tissue by a single solid tissue graft is sufficient to improve motor asymmetry in unilateral 6-OHDA-lesioned rats.

Atmospheric carbon dioxide concentrations over the past 60 million years

Knowledge of the evolution of atmospheric carbon dioxide concentrations throughout the Earth's history is important for a reconstruction of the links between climate and radiative forcing of the Earth's surface temperatures. Although atmospheric carbon dioxide concentrations in the early Cenozoic era (about 60 Myr ago) are widely believed to have been higher than at present, there is disagreement regarding the exact carbon dioxide levels, the timing of the decline and the mechanisms that are most important for the control of CO2 concentrations over geological timescales. Here we use the boron-isotope ratios of ancient planktonic foraminifer shells to estimate the pH of surface-layer sea water throughout the past 60 million years, which can be used to reconstruct atmospheric CO2 concentrations. We estimate CO2 concentrations of more than 2,000 p.p.m. for the late Palaeocene and earliest Eocene periods (from about 60 to 52 Myr ago), and find an erratic decline between 55 and 40 Myr ago that may have been caused by reduced CO2 outgassing from ocean ridges, volcanoes and metamorphic belts and increased carbon burial. Since the early Miocene (about 24 Myr ago), atmospheric CO2 concentrations appear to have remained below 500 p.p.m. and were more stable than before, although transient intervals of CO2 reduction may have occurred during periods of rapid cooling approximately 15 and 3 Myr ago.

Changes in the proportions of peripheral blood lymphocytes in patients with worn implants

We compared the peripheral blood and periprosthetic tissues of 53 patients at revision arthroplasty with those of 30 patients at primary arthroplasty to determine whether there is a systemic difference in lymphocytes in patients with worn hip implants. The absolute number and relative proportion of lymphocytes bearing CD2, CD3, CD4, CD8, CD16, CD19, HLA-DR, kappa and lambda antigens were compared with the levels of IL-1beta, IL-6 and PGE2 in the pseudosynovial membrane as well as with a semiquantitative estimate of metal and polyethylene particles, necrosis and chronic inflammation and the total concentration of metals within the periprosthetic tissues. There was a significant increase in the relative proportion of CD2-positive T-cells and CD16-positive natural killer cells in the peripheral blood at revision arthroplasty compared with primary arthroplasty and an increased proportion of CD8-positive T-cells and a decreased ratio of CD4 to CD8 (helper inducer/suppressor cytotoxic cells). Three control patients, who went on to have revision surgery, had values at primary arthroplasty which were similar to those of patients at the time of revision surgery. These differences did not correlate with the local concentration of metal, plastic or cement or inflammatory response or the type of prosthesis. An inverse correlation was noted between the necrosis in the periprosthetic tissue and both the local production of IL-6 and the absolute numbers of T-cells in peripheral blood. We conclude that there may be several cell-mediated systemic immune responses to aseptic loosening, at least one of which may be directly related to events in the periprosthetic tissues. We cannot exclude the possibility that the changes in the proportion of CD8-positive cells reflected a predisposition, rather than a reaction, to loosening of the implant.

Turkish honeybees: genetic variation and evidence for a fourth lineage of Apis mellifera mtDNA

The mtDNA of bees from 84 colonies of Turkish honeybees (Apis mellifera) was surveyed for variation at four diagnostic restriction sites and the sequence of a noncoding intergenic region. These colonies came from 16 locations, ranging from European Turkey and the western Mediterranean coast to the Caucasus Mountains along the Georgian border, the eastern Lake Van region, and the extreme south. Combined restriction site and sequence data revealed four haplotypes. Three haplotypes belonged to the eastern Mediterranean mtDNA lineage. The fourth haplotype, which had a novel restriction site pattern and noncoding sequence, was found in samples from the extreme south, near the Syrian border. We found two different noncoding sequences among the eastern Mediterranean haplotypes. The "Caucasian" sequence matches that described from A. m. caucasica, and the "Anatolian" sequence matches that of A. m. carnica. The frequency of the "Caucasian" sequence was highest (98-100%) in sites near the Georgian border and decreased steeply to the south and west. Elsewhere the Anatolian sequence was found. In European Turkey (Thrace) a restriction site polymorphism previously reported from A. m. carnica in Austria and the Balkans was present at high frequency. A novel mtDNA haplotype with a unique restriction site pattern and noncoding sequence was found among bees from Hatay, in the extreme south near the Syrian border. This haplotype differed from the three previously known lineages of honeybee mtDNA--African, western European, and eastern Mediterranean-and may represent a fourth mitochondrial lineage.

Multiple single-unit recordings in the striatum of freely moving animals: effects of apomorphine and D-amphetamine in normal and unilateral 6-hydroxydopamine-lesioned rats

Ensembles of striatal neurons were recorded in freely moving normal and unilateral 6-hydroxydopamine (6-OHDA)-lesioned rats using chronically implanted electrode arrays. Animals received bilateral striatal implants of two 16-microwire arrays 1 week before recordings. Identified striatal neurons were categorized as medium spiny-like and large aspiny-like based on a combination of their activity autocorrelations and firing rates. Baseline firing rates of medium spiny-like neurons in the 6-OHDA-lesioned striata were significantly faster than were firing rates of the same neurons in the intact hemispheres of 6-OHDA-lesioned rats or normal animals. However, firing rates of large aspiny-like neurons were faster in both hemispheres of the 6-OHDA-lesioned rats as compared to normal animals. Interestingly, firing rates of neurons in all groups decreased by fivefold or greater under urethane anesthesia, although the relative firing rates between hemispheres were unchanged. d-Amphetamine (5.0 mg/kg, s.c.) increased the firing rates of both types of striatal neurons by twofold or greater in normal rats and in the intact hemispheres of 6-OHDA-lesioned animals. By contrast, this treatment did not alter neuron firing in the 6-OHDA-lesioned striata. Apomorphine (0.05 mg/kg, s.c.) did not affect neuronal firing rates either in normal rat striatum or in the unlesioned hemispheres of 6-OHDA-lesioned animals. However, it did significantly increase the firing rate of the medium spiny-like neurons in 6-OHDA-lesioned striata. These results demonstrate that the dopaminergic innervation of the striatum differentially influences two electrophysiologically distinct sets of striatal neurons in freely moving rats.

Middle eocene seawater pH and atmospheric carbon dioxide concentrations

The carbon dioxide content of the atmosphere [measured as the partial pressure of CO2 (pCO2)] affects the content of the surface ocean, which in turn affects seawater pH. The boron isotope composition (delta11B) of contemporaneous planktonic foraminifera that calcified their tests at different water depths can be used to reconstruct the pH-depth profile of ancient seawater. Construction of a pH profile for the middle Eocene tropical Pacific Ocean shows that atmospheric pCO2 was probably similar to modern concentrations or slightly higher.

Potentiation of ethanol effects in cerebellum by activation of endogenous noradrenergic inputs

We previously found that beta adrenergic agonists such as norepinephrine and isoproterenol potentiate the depressant actions of ethanol (EtOH) on cerebellar Purkinje neurons. Furthermore, antagonism of the beta adrenergic effects of endogenously released catecholamines with timolol reduced EtOH-induced depressions of neuronal activity in that brain area. In the present study, we further investigated the hypothesis that activity of the endogenous noradrenergic innervation to the cerebellar cortex can potentiate this EtOH action. We investigated the interaction of synaptically released catecholamines on EtOH-induced depressions of cerebellar Purkinje neurons in three different experiments: (1) endogenous catecholamine release was facilitated by applying the catecholamine uptake inhibitor desmethylimipramine, (2) activity of the noradrenergic innervation of the cerebellar cortex from locus ceruleus was increased by causing acute withdrawal from 7 days of chronic morphine treatment with the opiate antagonist naloxone, and (3) the noradrenergic innervation of the cerebellum was activated directly by electrical stimulation of the locus ceruleus. We found that all three conditions potentiated EtOH-induced depressions in the cerebellum and that this potentiation of ethanol effects could be antagonized by the systemic administration of the beta adrenergic antagonist propranolol. Furthermore, morphine withdrawal also caused potentiation of the depressant effects of phencyclidine, which are known to be regulated by the endogenous catecholamine innervation in this brain area. Taken together with our previous data demonstrating a beta adrenergic facilitation of EtOH actions in this brain area, the present results suggest that the activity of endogenous noradrenergic synapses can regulate the depressant effects of EtOH on cerebellar Purkinje neurons.

Reconstructing past ocean pH-depth profiles

Measurement of boron isotope compositions in species of planktonic foraminifera that calcified their tests at different depths in the water column are used to reconstruct the pH profile of the upper water column of the tropical ocean. Results for five time windows from the middle Miocene to the late Pleistocene indicate pH-depth profiles similar to that of the modern ocean in this area, which suggests that this method may greatly aid in our understanding of the global carbon cycle.

Electrophysiological characterization of cerebellar neurons from adult rats exposed to ethanol during development

The purpose of this study was to investigate the spontaneous activity of mature rat cerebellar neurons that had been exposed to ethanol (EtOH) during postnatal days 4 to 10, which corresponds to the third trimester in humans. Newborn Sprague-Dawley rats were implanted with gastric feeding tubes and were artificially reared from postnatal days 4 to 10 with two different diets. The experimental group received 4.5 g/kg/day of EtOH delivered in a milk solution. Controls received similar feeding with an isocaloric supplement replacing the EtOH. Electrophysiological evaluations were performed after an EtOH-free rearing period. Although lobules IX and X of the cerebellar vermis appeared morphologically smaller in the animals neonatally exposed to EtOH, compared with controls, extracellular recordings from both Purkinje cells and Golgi interneurons in adult rats showed no differences in spontaneous activity or firing pattern between the control and EtOH-exposed animals. Similarly, excitations and inhibitions of Purkinje neuron activity evoked by parallel pathway stimulation appeared unaffected by the developmental EtOH exposure. However, we did observe a significant decrease in the proportion of Purkinje neurons generating complex spike bursts in the group exposed to EtOH neonatally. These data suggest that, although fewer Purkinje neurons may survive the brain growth spurt if exposed to EtOH during this critical period of development, those that do survive appear to function normally. The observed abnormality in complex spike production may result from EtOH effects on developing neurons in the inferior olive that give rise to the climbing fibers that cause this bursting pattern in Purkinje neurons.

Characterization of wear debris associated with aseptic loosening of a canine hip prosthesis

A 12-month-old Golden Retriever bitch underwent unilateral hip arthroplasty following a diagnosis of coxofemoral osteoarthritis secondary to hip dysplasia. The hip prosthesis underwent aseptic loosening and was removed 6 months after implantation. Synovial biopsies taken at that time revealed scattered foci of granulomatous inflammation associated with intra-cytoplasmic and extracellular particulate material. Electron microscopical analyses demonstrated that this material contained cobalt, chromium, titanium and zirconium, which was probably wear debris from the loosened prosthesis. In human patients with hip arthroplasty, widespread dissemination of wear debris from loosened prostheses occasionally occurs, with an increased prevalence of neoplasia. A similar phenomenon may be predicted to occur with the increasing use of hip arthroplasty in the dog.

Effects of ethanol on striatal dopamine overflow and clearance: an in vivo electrochemical study

Previous studies have shown that the neurotransmitter dopamine (DA) is implicated in the reinforcing effects of ethanol and other abused drugs. Ethanol also alters DA overflow and uptake in vivo. Further studies of the role of DA in the behavioral and neurochemical effects of ethanol may help explain the pharmacological mechanisms by which these effects are produced. In these studies we used in vivo electrochemical recordings to investigate the effects of ethanol (EtOH) on the dynamics of evoked DA overflow and DA uptake in rat dorsal striatum. Local applications of EtOH from a multibarrel micropipette did not produce detectable changes in extracellular levels of endogenous DA in the dorsal striatum. EtOH application did attenuate potassium (K+)-evoked overflow of DA in a time-dependent fashion. In contrast, tyramine-induced DA overflow, a calcium-independent process thought to be carrier mediated, was not altered by local EtOH application in the dorsal striatum. Striatal uptake of locally applied exogenous DA was decreased by nomifensine, an effect that was attenuated by locally applied EtOH. Taken together, these data suggest that one of the effects of EtOH on DA-containing nerve endings in the rat striatum involves functional changes in the high-affinity DA transporter associated with these nerve endings.

Glial cell line-derived neurotrophic factor improves survival of ventral mesencephalic grafts to the 6-hydroxydopamine lesioned striatum

One approach to replace lost dopaminergic neurons in Parkinson's disease is to transplant fetal mesencephalic tissue into the striatum. In an attempt to expand the developmental window useful for grafting of mesencephalic tissue and increase the fiber outgrowth from grafted dopaminergic neurons, we have pretreated fetal mesencephalic tissue with the dopaminotrophic factor glial cell line-derived neurotrophic factor (GDNF). Mesencephalic tissue pieces from embryonic day 18-19 Fischer 344 rats were preincubated for 20 min with GDNF (1 microg/microl) or vehicle. Two tissue pieces were then transplanted into the striatum of rats that had been unilaterally lesioned by medial forebrain bundle injections of 6-hydroxydopamine. The animals were tested for apomorphine-induced rotations prior to intracranial grafting. Host rats received intrastriatal injections of 10 microg GDNF or control solution at 10 days and 4 weeks postgrafting. The animals were tested in the rotometer twice monthly following transplantation. Despite the fact that these transplants were from a suboptimal donor stage, the rotations were significantly decreased in both transplanted groups. Immunohistochemical evaluation of the host brains revealed that the overall size of transplanted mesencephalic tissue was significantly increased in the GDNF-treated animals, and that the average size of transplanted tyrosine hydroxylase (TH)-positive neurons was also increased. Furthermore, we found that the innervation density of surrounding host striatal tissue was significantly increased in the GDNF-treated group, as compared with controls. Taken together, these results suggest that treatment of intrastriatal ventral mesencephalon grafts with GDNF can optimize the conditions for intracranial grafting and thus improve the chances for functional recovery following the intrastriatal grafting procedure.

Effects of ethanol and nomifensine on NE clearance in the cerebellum of young and aged Fischer 344 rats

Rapid chronoamperometric recordings coupled with local application of drugs by pressure ejection were used to investigate the effects of nomifensine and ethanol (EtOH) on exogenous norepinephrine (NE) clearance in the cerebellum of young (5-month-old) and aged (24-26-month-old) male Fischer 344 rats. In the young rats, local nomifensine application prolonged exogenous NE clearance, indicating transporter mediated uptake inhibition. NE clearance was modestly but significantly prolonged in the aged rats as compared to the young rats, suggesting less efficient uptake. Consistent with this, there was little effect of nomifensine on NE clearance in the aged rats. In contrast to the effect of nomifensine, EtOH inhibited NE clearance in both young and aged rats. These data further support the hypothesis that one effect of EtOH in cerebellar NE systems is inhibition of NE uptake into NE-containing nerve terminals, and they also demonstrate that the effect of nomifensine on exogenous NE clearance in vivo in the cerebellum is altered by the aging process, while the effect of EtOH is not.

Functional interactions between spinal cord grafts suggest asymmetries dictated by graft maturity

Fetal spinal cord tissue grafts have been advocated as a possible repair strategy for spinal cord injury. In the present study, we used intraocular spinal cord grafts to model the interactions which may occur between fetal and adult spinal cord after making such a graft and to study to which extent functional connections can be expected to occur between the host and graft tissue. We first grafted fetal spinal cord to the anterior chamber of the eye where it was allowed to mature. A second piece of fetal spinal cord was then sequentially grafted in contact with the first graft. Electrophysiological recordings made from the older graft while electrically stimulating the younger graft provided evidence for an excitatory innervation from the younger spinal cord graft to the mature spinal cord which appeared to be glutamatergic. However, we only rarely found excitatory inputs from the first, mature spinal cord graft to the younger graft. Fiber connections between the two spinal cord grafts were verified by retrograde tracing and neurofilament immunohistochemistry. In no case was a trophic influence on graft volume observed between spinal cord grafts regardless of whether the transplantations were performed sequentially or at the same time. Even the introduction of a second graft to immature spinal cord tissue was ineffective. In contrast, we found a marked trophic, neuron-rescuing effect of spinal cord grafts upon cografts of fetal dorsal root ganglia. This latter observation is consistent with the hypothesis that spinal cord tissue can exert a trophic effect on developing sensory ganglia and demonstrates that many sensory neurons can survive in the presence of a central target and in the absence of the appropriate peripheral target. These intraocular experiments predict that fetal spinal cord grafted to the injured adult spinal cord may develop effective excitatory inputs with the host, while host-to-graft inputs may develop to a considerably smaller extent. Our results also suggest that the adult spinal cord does not exert marked trophic effects on growth of fetal spinal cord, while it does exert a trophic influence on central projections of dorsal root ganglia.

Beta adrenergic sensitization of gamma-aminobutyric acid receptors to ethanol involves a cyclic AMP/protein kinase A second-messenger mechanism

Previous studies have found that ethanol (EtOH) will consistently potentiate gamma-aminobutyric acid (GABA) receptor function in the cerebellum during beta adrenergic receptor activation. One consequence of beta adrenergic receptor stimulation is to increase cAMP levels, which, in turn, activate protein kinase A (PKA)-mediated phosphorylation of intracellular protein sites. In the present study, we investigated three cAMP analogues, two activators and one inhibitor of PKA to determine whether this cAMP-mediated second-messenger system may be one mechanism involved in the previously observed beta adrenergic interaction of EtOH with the GABA(A) receptor. Furthermore, because the phosphorylation state of the GABA(A) receptor may be an important determinant of function, we investigated the effect of the block of phosphatase activity on EtOH/GABA receptor interactions. We found that similar to the beta adrenergic agonist isoproterenol, local applications of the membrane-permeable cAMP analogues 8-bromo-cAMP and Sp-cAMP could modulate responses to iontophoretically applied GABA and that these modulated GABA responses were sensitized to the potentiative effects of EtOH. EtOH did not facilitate unmodulated GABA effects or GABA responses that were maximally modulated by 8-bromo-cAMP, suggesting that the cAMP mechanism mediates the observed EtOH interaction with GABA mechanisms. Furthermore, the PKA inhibitor Rp-cAMP reversed the EtOH-induced potentiation of the isoproterenol-modulated GABA responses. Finally, microcystin-LR and okadaic acid, which are type I and IIa phosphatase inhibitors, could also modulate and sensitize GABA responses to EtOH. These data suggest that beta adrenergic sensitization of GABA(A) receptors to EtOH involves the intracellular cAMP/PKA second-messenger cascade.

Differential development and characterization of rapid acute neuronal tolerance to the depressant effects of ethanol on cerebellar Purkinje neurons of low-alcohol-sensitive and high-alcohol-sensitive rats

Rapid acute neuronal tolerance (RANT) to the depressant effects of ethanol (EtOH) is a desensitization of EtOH-induced depression of neuronal firing that develops over the first 5 to 7 min of EtOH exposure. This phenomenon has been hypothesized to play a role in acute behavioral insensitivity to EtOH and is expressed by cerebellar Purkinje neurons in animals selectively bred for insensitivity to EtOH-induced ataxia, such as low-alcohol-sensitive (LAS) rats and short-sleep mice. Purkinje neurons of animals bred for high sensitivity to EtOH-induced behavioral ataxia, such as high-alcohol-sensitive (HAS) rats and long-sleep mice, only infrequently express such acute tolerance to EtOH-induced depression of neuronal activity. However, because higher EtOH doses are required to depress Purkinje neuron activity in LAS rats than in HAS rats, it was not known whether the higher EtOH doses that depress LAS neurons would also induce RANT to EtOH in HAS rats, which were generally not exposed to such high EtOH doses in previous studies. Furthermore, the conditions for development and maintenance of RANT to EtOH had not been characterized. We found that RANT to EtOH-induced depression of cerebellar neurons principally developed within 5 min of EtOH application and recovered within 20 min of the last EtOH exposure and that neurons in HAS rats did not develop acute tolerance to the higher EtOH doses that were effective in LAS rats. We conclude that this rapid tolerance contributes to the acute EtOH sensitivity difference between LAS and HAS rats.

Ethanol depression of cerebellar Purkinje neuron firing involves nicotinic acetylcholine receptors

Local application of ethanol (EtOH) has been reported to inhibit Purkinje neuron firing. EtOH-induced depressions can be antagonized by bicuculline, suggesting involvement of GABAA receptors. Since there is evidence from other studies indicating that nicotine may interact with EtOH responses, in this study we investigated whether nicotinic acetylcholine receptors (nAChR's) might be also involved in EtOH-induced depressions of these neurons in urethane-anesthetized Sprague-Dawley rats. Using local application (micropressure ejection) of drugs onto cerebellar Purkinje neurons while recording extracellular firing rates, we found that depressant responses to EtOH could be potentiated by subdepressant doses of nicotine. Furthermore, EtOH-induced depressions of firing could be antagonized by mecamylamine, a nicotinic acetylcholine receptor (nAChR) antagonist. Results from the present study indicate that EtOH-induced depressions may involve nAChRs in the cerebellum.

8-Bromo-cAMP mimics beta-adrenergic sensitization of GABA responses to ethanol in cerebellar Purkinje neurons in vivo

Previous studies in our laboratory indicated that electrophysiological responses of cerebellar Purkinje neurons to GABA were not routinely potentiated by ethanol (EtOH), and the potentiation was not large when it occurred. In the presence of beta-adrenergic agonists, such as isoproterenol, however, GABA inhibitions became sensitive to potentiation by EtOH in nearly every Purkinje neuron tested. beta-adrenergic receptor activation alone also modulates (potentiates) GABA responses on Purkinje neurons, and this has been reported to be mediated by a cAMP second messenger system. Herein, we report that the membrane-permeable cAMP analog, 8-bromoadenosine-3',5'-cyclic monophosphate (8-Br-cAMP), but not the membrane-impermeable cAMP, can also modulate GABA responses and that EtOH potentiates this facilitatory action of 8-Br-cAMP. These effects are not likely caused by adenosine receptor mechanisms, because this 8-bromoadenosine mediated modulation and sensitization was observed in the presence of systemic theophylline. These data suggest that the beta-adrenergic modulation and sensitization to EtOH of cerebellar Purkinje neuron GABA responses occur via a cAMP second messenger mechanism.

Ethanol-induced depressions of cerebellar Purkinje neurons are potentiated by beta-adrenergic mechanisms in rat brain

Electrophysiological studies indicate that EtOH decreases the firing rate of cerebellar Purkinje neurons in vivo and in vitro through a GABAA mechanism. These neurons receive a prominent noradrenergic input from the locus coeruleus. Stimulation of the locus coeruleus or local application of beta-adrenergic agonists potentiates Purkinje neuron responses to GABA and sensitizes GABA responses to the potentiative effects of EtOH. In the present study, we found that the modulatory influences of the beta-adrenergic agonist isoproterenol potentiated EtOH-induced depressions of Purkinje neuron firing. This isoproterenol interaction with EtOH was antagonized by the beta-adrenergic antagonist timolol. We found evidence that endogenous catecholamines can cause this effect as well. Timolol antagonized EtOH-induced depressions on 20% of the neurons studied. This was the same frequency as that previously found for EtOH-induced potentiations of GABA depressions in this brain area. These data suggest that the Purkinje neurons showing this interaction receive spontaneously active catecholamine inputs that sensitize the GABA effects to the potentiative effects of ethanol. Consistent with this hypothesis, we also found that timolol antagonized this GABA/EtOH interaction. Taken together, these results are consistent with the hypothesis that EtOH-induced depressions of Purkinje neurons involved endogenous GABA actions that may be regulated by beta-adrenergic mechanisms.

Spinal cord-skeletal muscle cografts: trophic and functional interactions

Skeletal muscle from embryonic day 20 (E20) was combined with E15 rat spinal cord in the anterior chamber of the eye of adult albino rats. The two grafts were either transplanted concomitantly or sequentially, in which case muscle tissue was added 4 months after the spinal cord. Control groups received a single graft of either spinal cord or skeletal muscle. Survival and intraocular growth were observed through the cornea. After maturation in oculo, the double grafts were examined immunohistologically utilizing antisera to neurofilament (NF) and acetylcholinesterase (AChE). The grafts were also evaluated using electrical stimulation to determine functional connectivity. The spinal cord and skeletal muscle grafts were found to exert reciprocal trophic effects on each other, evidenced as a larger muscle mass in skeletal muscle grafts allowed to develop in the presence of spinal cord tissue, and a larger volume of spinal cord grafts allowed to develop together with a skeletal muscle graft, respectively. Immunohistochemistry revealed NF-positive nerve fibers leaving the spinal cord graft and entering the muscle tissue. AChE-positive endplates developed in the muscle grafts. Electrical stimulation of the spinal cord part of double-graft combinations generally elicited contractile responses in specific areas of the muscle cograft. These results demonstrate both structural and functional connections between grafts of spinal cord and skeletal muscle tissue in vivo. The fact that such connections were also established between a mature (adult) spinal cord graft and fetal skeletal muscle tissue suggests that some alpha-motoneurons are able to survive for many months in the intraocular grafts without an appropriate target, and that they are able to subsequently innervate skeletal muscle targets.

Widespread dissemination of metal debris from implants

In a post-mortem study, we compared subjects with metal implants with and without visible wear with an age-matched control group to determine the extent and effects of dissemination of wear debris. In subjects with stainless-steel and cobalt-chrome prostheses metal was found in local and distant lymph nodes, bone marrow, liver and spleen. The levels were highest in subjects with loose, worn joint prostheses and the main source of the debris was the matt coating. Metal levels were also raised in subjects with implants without visible wear and, to a less extent, in those with dynamic hip screws. Necrosis of lymph nodes was seen in those cases with the most wear, and potential damage to more distant organs such as the bone marrow, liver and spleen in the long term cannot be discounted. The consequences for the immune system and the role of metal dissemination in the possible induction of neoplasia are discussed.

Widespread dissemination of metal debris from implants

In a post-mortem study, we compared subjects with metal implants with and without visible wear with an age-matched control group to determine the extent and effects of dissemination of wear debris. In subjects with stainless-steel and cobalt-chrome prostheses metal was found in local and distant lymph nodes, bone marrow, liver and spleen. The levels were highest in subjects with loose, worn joint prostheses and the main source of the debris was the matt coating. Metal levels were also raised in subjects with implants without visible wear and, to a less extent, in those with dynamic hip screws. Necrosis of lymph nodes was seen in those cases with the most wear, and potential damage to more distant organs such as the bone marrow, liver and spleen in the long term cannot be discounted. The consequences for the immune system and the role of metal dissemination in the possible induction of neoplasia are discussed.

Ethanol inhibits the uptake of exogenous norepinephrine from the extracellular space of the rat cerebellum

Rapid chronoamperometric recordings using nafion-coated carbon fiber electrodes coupled with pressure-ejection of drugs were used to investigate the effects of ethanol on norepinephrine (NE)-containing nerve terminals in the urethane-anesthetized Fischer 344 rat. Local application of ethanol from a double-barrel micropipette did not produce detectable changes in extracellular levels of NE in the rat cerebellar cortex. However, when ethanol was applied prior to local application of NE, it was seen to inhibit the uptake of NE from the extracellular space. These results were compared to the effects seen from the local application of a known high-affinity uptake inhibitor, nomifensine. Nomifensine was found to inhibit the extracellular uptake of NE in rat cerebeller cortex similar to ethanol. Our results support the hypothesis that one effect of ethanol on the noradrenergic system of the rat cerebellum is an alteration in the uptake of NE into NE-containing nerve endings. In addition, the present data concerning ethanol-induced inhibition of NE clearance or uptake support our previous electrophysiological studies in which we found that ethanol can potentiate the modulatory effects of beta-agonists on GABA responses of cerebellar Purkinje neurons.

Differential effects of ethanol on the firing rates of Golgi-like neurons and Purkinje neurons in cerebellar slices in vitro

Previous studies have demonstrated that ethanol (EtOH) inhibits the firing rate of Purkinje neurons both in vitro and in vivo. However, little is known about the response of cerebellar interneurons to EtOH. In this report, we describe the effects of locally applied EtOH on the firing of one type of cerebellar interneuron, tentatively identified as Golgi neurons, and on Purkinje cells in brain slices in vitro. The Golgi neurons were excited by EtOH, whereas EtOH depressed the firing rate of Purkinje neurons. To the best of our knowledge, this is the first report of responses of cerebellar Golgi neurons to local applications of EtOH.

The use of magnetic resonance imaging in monitoring interferon therapy of multiple sclerosis

Magnetic resonance imaging (MRI) was used to evaluate the efficacy of systemic lymphoblastoid interferon therapy in chronic progressive multiple sclerosis. The clinical outcome of this trial has been reported previously. Thirty-six patients with chronic progressive multiple sclerosis were treated with interferon daily for 6 months and 27 received placebo. Patients had MRI at the outset of the study and after 6 and 24 months. Lesion activity and changes in lesion load were determined. As the study progressed, both the interferon- and the placebo-treated group developed more active lesions. There was no difference in lesion activity between the two groups. Comparison of lesion load, however, showed a trend toward improvement after 6 months for the interferon-treated group. This difference between the two groups had disappeared by the end of the study. We conclude that lymphoblastoid interferon was not effective in decreasing active MRI-detected lesions or in decreasing MRI lesion load in patients with chronic progressive multiple sclerosis.