Universal DNA methylation age across mammalian tissues

Aging, often considered a result of random cellular damage, can be accurately estimated using DNA methylation profiles, the foundation of pan-tissue epigenetic clocks. Here, we demonstrate the development of universal pan-mammalian clocks, using 11,754 methylation arrays from our Mammalian Methylation Consortium, which encompass 59 tissue types across 185 mammalian species. These predictive models estimate mammalian tissue age with high accuracy (r > 0.96). Age deviations correlate with human mortality risk, mouse somatotropic axis mutations and caloric restriction. We identified specific cytosines with methylation levels that change with age across numerous species. These sites, highly enriched in polycomb repressive complex 2-binding locations, are near genes implicated in mammalian development, cancer, obesity and longevity. Our findings offer new evidence suggesting that aging is evolutionarily conserved and intertwined with developmental processes across all mammals.

DNA methylation networks underlying mammalian traits

Using DNA methylation profiles (n = 15,456) from 348 mammalian species, we constructed phyloepigenetic trees that bear marked similarities to traditional phylogenetic ones. Using unsupervised clustering across all samples, we identified 55 distinct cytosine modules, of which 30 are related to traits such as maximum life span, adult weight, age, sex, and human mortality risk. Maximum life span is associated with methylation levels in HOXL subclass homeobox genes and developmental processes and is potentially regulated by pluripotency transcription factors. The methylation state of some modules responds to perturbations such as caloric restriction, ablation of growth hormone receptors, consumption of high-fat diets, and expression of Yamanaka factors. This study reveals an intertwined evolution of the genome and epigenome that mediates the biological characteristics and traits of different mammalian species.

Stuck in a corner: Anthropogenic noise threatens narwhals in their once pristine Arctic habitat

Niche-conservative species are especially susceptible to changes in their environment, and detecting the negative effects of new stressors in their habitats is vital for safeguarding of these species. In the Arctic, human disturbance including marine traffic and exploration of resources is increasing rapidly due to climate change-induced reduction of sea ice. Here, we show that the narwhal, Monodon monoceros, is extremely sensitive to human-made noise. Narwhals avoided deep diving (> 350 m) with simultaneous reduction of foraging and increased shallow diving activity as a response to either ship sound alone or ship sound with concurrent seismic airgun pulses. Normal behavior decreased by 50 to 75% at distances where received sound levels were below background noise. Narwhals were equally responsive to both disturbance types, hence demonstrating their acute sensitivity to ship sound. This sensitivity coupled with their special behavioral-ecological strategy including a narrow ecological niche and high site fidelity makes them thus especially vulnerable to human impacts in the Arctic.

DNA methylation based biomarkers for aging long-lived cetaceans

Epigenetic approaches for estimating the age of living organisms are revolutionizing studies of long-lived species. Molecular biomarkers that allow age estimates from small tissue biopsies promise to enhance studies of long-lived whales; addressing a fundamental and challenging parameter in wildlife management. DNA methylation (DNAm) can affect gene expression, and strong correlations between DNAm patterns and age have been documented in humans and non-human vertebrates and used to construct "epigenetic clocks". We present several epigenetic clocks for skin samples from two of the longest lived cetaceans, killer whales and bowhead whales. Applying the mammalian methylation array to genomic DNA from skin samples we validate four different clocks with median errors of 2.3 - 3.7 years. These epigenetic clocks demonstrate the validity of using cytosine methylation data to estimate the age of long-lived cetaceans, and have broad applications supporting the conservation and management of long-lived cetaceans using genomic DNA from remote tissue biopsies.

Combining δ13C and δ15N from bone and dentine in marine mammal palaeoecological research: insights from toothed whales

Stable carbon (δ¹³C) and nitrogen (δ¹⁵N) isotopic compositions of bone and dentine collagen extracted from museum specimens have been widely used to study the paleoecology of past populations. Due to possible systematic differences in stable isotope values between bone and dentine, dentine values need to be transformed into bone-collagen equivalent using a correction factor to allow comparisons between the two collagen sources. Here, we provide correction factors to transform dentine δ¹³C and δ¹⁵N values into bone-collagen equivalent for two toothed whales: narwhal and beluga. We sampled bone and dentine from the skulls of 11 narwhals and 26 belugas. In narwhals, dentine was sampled from tusk and embedded tooth; in belugas, dentine was sampled from tooth. δ¹³C and δ¹⁵N were measured, and intra-individual bone and dentine isotopic compositions were used to calculate correction factors for each species. We detected differences in δ¹³C and δ¹⁵N. In both narwhals and belugas, we found lower average δ¹³C and δ¹⁵N in bone compared with dentine. The correction factors provided by the study enable the combined analysis of stable isotope data from bone and dentine in these species.

Narwhals react to ship noise and airgun pulses embedded in background noise

Anthropogenic activities are increasing in the Arctic, posing a threat to niche-conservative species with high seasonal site fidelity, such as the narwhal Monodon monoceros. In this controlled sound exposure study, six narwhals were live-captured and instrumented with animal-borne tags providing movement and behavioural data, and exposed to concurrent ship noise and airgun pulses. All narwhals reacted to sound exposure with reduced buzzing rates, where the response was dependent on the magnitude of exposure defined as 1/distance to ship. Buzzing rate was halved at 12 km from the ship, and whales ceased foraging at 7-8 km. Effects of exposure could be detected at distances > 40 km from the ship.At only a few kilometres from the ship, the received high-frequency cetacean weighted sound exposure levels were below background noise indicating extreme sensitivity of narwhals towards sound disturbance and demonstrating their ability to detect signals embedded in background noise. The narwhal's reactions to sustained disturbance may have a plethora of consequences both at individual and population levels. The observed reactions of the whales demonstrate their auditory sensitivity but also emphasize, that anthropogenic activities in pristine narwhal habitats needs to be managed carefully if healthy narwhal populations are to be maintained.

Analysis of narwhal tusks reveals lifelong feeding ecology and mercury exposure

The ability of animals to respond to changes in their environment is critical to their persistence. In the Arctic, climate change and mercury exposure are two of the most important environmental threats for top predators.^1-3 Rapid warming is causing precipitous sea-ice loss, with consequences on the distribution, composition, and dietary ecology of species^4-7 and, thus, exposure to food-borne mercury.⁸ Current understanding of global change and pollution impacts on Arctic wildlife relies on single-time-point individual data representing a snapshot in time. These data often lack comprehensive temporal resolution and overlook the cumulative lifelong nature of stressors as well as individual variation. To overcome these challenges, we explore the unique capacity of narwhal tusks to characterize chronological lifetime biogeochemical profiles, allowing for investigations of climate-induced dietary changes and contaminant trends. Using temporal patterns of stable isotopes (δ¹³C and δ¹⁵N) and mercury concentrations in annually deposited dentine growth layer groups in 10 tusks from Northwest Greenland (1962-2010), we show surprising plasticity in narwhal feeding ecology likely resulting from climate-induced changes in sea-ice cover, biological communities, and narwhal migration. Dietary changes consequently impacted mercury exposure primarily through trophic magnification effects. Mercury increased log-linearly over the study period, albeit with an unexpected rise in recent years, likely caused by increased emissions and/or greater bioavailability in a warmer, ice-free Arctic. Our findings are consistent with an emerging pattern in the Arctic of reduced sea-ice leading to changes in the migration, habitat use, food web, and contaminant exposure in Arctic top predators.

Population-specific sex and size variation in long-term foraging ecology of belugas and narwhals

Intraspecific variation in resource use by individuals of different age, sex or size may reflect differing energetic requirements and physiological constraints. Males and females often show differences in diet owing to sexual size dimorphism, different life histories and/or habitat use. Here, we investigate how sex and size influence the long-term foraging ecology of belugas and narwhals in Greenland, using stable isotopes of carbon and nitrogen from bone collagen. We show that males have a higher trophic level and a larger ecological niche than females in West Greenland belugas and in East Greenland narwhals. In addition, for these two populations, we find that δ ¹⁵N increases with size, particularly in males. We hypothesize that sexual size dimorphism together with strong maternal investment drive these differences. By contrast, we find no differences in foraging ecology between sexes in West Greenland narwhals and observe no influence of size on trophic level. This may reflect the influence of interspecific competition in West Greenland, where the distributions of belugas and narwhals overlap, and/or geographical resource partitioning among different summer aggregations of narwhals. Our results suggest that sex and size variations in diet are population dependent, and probably the result of varying ecological interactions.

The impact of rising sea temperatures on an Arctic top predator, the narwhal

Arctic top predators are expected to be impacted by increasing temperatures associated with climate change, but the relationship between increasing sea temperatures and population dynamics of Arctic cetaceans remains largely unexplored. Narwhals (Monodon monoceros) are considered to be among the most sensitive of Arctic endemic marine mammals to climate change due to their limited prey selection, strict migratory patterns and high site fidelity. In the context of climate change, we assume that the population dynamics of narwhals are partly influenced by changes in environmental conditions, with warm areas of increasing sea temperatures having lower abundance of narwhals. Using a unique large dataset of 144 satellite tracked narwhals, sea surface temperature (SST) data spanning 25 years (1993–2018) and narwhal abundance estimates from 17 localities, we (1) assessed the thermal exposure of this species, (2) investigated the SST trends at the summer foraging grounds, and (3) assessed the relationship between SST and abundance of narwhals. We showed a sharp SST increase in Northwest, Mideast and Southeast Greenland, whereas no change could be detected in the Canadian Arctic Archipelago (CAA) and in the Greenland Sea. The rising sea temperatures were correlated with the smallest narwhal abundance observed in the Mideast and Southeast Greenland (< 2000 individuals), where the mean summer sea temperatures were the highest (6.3 °C) compared to the cold waters of the CAA (0.7 °C) that were associated with the largest narwhal populations (> 40,000 individuals). These results support the hypothesis that warming ocean waters will restrict the habitat range of the narwhal, further suggesting that narwhals from Mideast and Southeast Greenland may be under pressure to abandon their traditional habitats due to ocean warming, and consequently either migrate further North or locally go extinct.

Some like it cold: Temperature-dependent habitat selection by narwhals

The narwhal (Monodon monoceros) is a high-Arctic species inhabiting areas that are experiencing increases in sea temperatures, which together with reduction in sea ice are expected to modify the niches of several Arctic marine apex predators. The Scoresby Sound fjord complex in East Greenland is the summer residence for an isolated population of narwhals. The movements of 12 whales instrumented with Fastloc-GPS transmitters were studied during summer in Scoresby Sound and at their offshore winter ground in 2017-2019. An additional four narwhals provided detailed hydrographic profiles on both summer and winter grounds. Data on diving of the whales were obtained from 20 satellite-linked time-depth recorders and 16 Acousonde™ recorders that also provided information on the temperature and depth of buzzes. In summer, the foraging whales targeted depths between 300 and 850 m where the preferred areas visited by the whales had temperatures ranging between 0.6 and 1.5°C (mean = 1.1°C, SD = 0.22). The highest probability of buzzing activity during summer was at a temperature of 0.7°C and at depths > 300 m. The whales targeted similar depths at their offshore winter ground where the temperature was slightly higher (range: 0.7-1.7°C, mean = 1.3°C, SD = 0.29). Both the probability of buzzing events and the spatial distribution of the whales in both seasons demonstrated a preferential selection of cold water. This was particularly pronounced in winter where cold coastal water was selected and warm Atlantic water farther offshore was avoided. It is unknown if the small temperature niche of whales while feeding is because prey is concentrated at these temperature gradients and is easier to capture at low temperatures, or because there are limitations in the thermoregulation of the whales. In any case, the small niche requirements together with their strong site fidelity emphasize the sensitivity of narwhals to changes in the thermal characteristics of their habitats.

Influence of past climate change on phylogeography and demographic history of narwhals, Monodon monoceros

The Arctic is warming at an unprecedented rate, with unknown consequences for endemic fauna. However, Earth has experienced severe climatic oscillations in the past, and understanding how species responded to them might provide insight into their resilience to near-future climatic predictions. Little is known about the responses of Arctic marine mammals to past climatic shifts, but narwhals (Monodon monoceros) are considered one of the endemic Arctic species most vulnerable to environmental change. Here, we analyse 121 complete mitochondrial genomes from narwhals sampled across their range and use them in combination with species distribution models to elucidate the influence of past and ongoing climatic shifts on their population structure and demographic history. We find low levels of genetic diversity and limited geographic structuring of genetic clades. We show that narwhals experienced a long-term low effective population size, which increased after the Last Glacial Maximum, when the amount of suitable habitat expanded. Similar post-glacial habitat release has been a key driver of population size expansion of other polar marine predators. Our analyses indicate that habitat availability has been critical to the success of narwhals, raising concerns for their fate in an increasingly warming Arctic.

The longer the better: evidence that narwhal tusks are sexually selected

Once thought to be the magical horn of a unicorn, narwhal tusks are one of the most charismatic structures in biology. Despite years of speculation, little is known about the tusk's function, because narwhals spend most of their lives hidden underneath the Arctic ice. Some hypotheses propose that the tusk has sexual functions as a weapon or as a signal. By contrast, other hypotheses propose that the tusk functions as an environmental sensor. Since assessing the tusks function in nature is difficult, we can use the morphological relationships of tusk size with body size to understand this mysterious trait. To do so, we collected morphology data on 245 adult male narwhals over the course of 35 years. Based on the disproportional growth and large variation in tusk length we found, we provide the best evidence to date that narwhal tusks are indeed sexually selected. By combining our results on tusk scaling with known material properties of the tusk, we suggest that the narwhal tusk is a sexually selected signal that is used during male-male contests.

Narwhal Genome Reveals Long-Term Low Genetic Diversity despite Current Large Abundance Size

The narwhal (Monodon monoceros) is a highly specialized endemic Arctic cetacean, restricted to the Arctic seas bordering the North Atlantic. Low levels of genetic diversity have been observed across several narwhal populations using mitochondrial DNA and microsatellites. Despite this, the global abundance of narwhals was recently estimated at ∼170,000 individuals. However, the species is still considered vulnerable to changing climates due to its high specialization and restricted Arctic distribution. We assembled and annotated a genome from a narwhal from West Greenland. We find relatively low diversity at the genomic scale and show that this did not arise by recent inbreeding, but rather has been stable over an extended evolutionary timescale. We also find that the current large global abundance most likely reflects a recent rapid expansion from a much smaller founding population.

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Assembled and annotated narwhal nuclear genome

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Low genetic diversity despite large global abundance

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Lack of signs of inbreeding

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Demography is the driving force behind the low diversity

Accuracy of the Aspartic Acid Racemization Technique in Age Estimation of Mammals and the Influence of Body Temperature

The aspartic acid racemization (AAR) technique has been applied for age estimation of humans and other mammals for more than four decades. In this study, eye lenses from 124 animals representing 25 mammalian species were collected and D/L ratios obtained using the AAR technique. The animals were either of known age or had the age estimated by other methods. The purpose of the study was to: a) estimate the accuracy of the AAR technique, and b) examine the effect of body temperature on racemization rates. Samples from four of the 25 species covered the range of ages that is needed to estimate species-specific racemization rates. The sample size from a single species of known age, the pygmy goat (Capra hircus, n = 35), was also large enough to investigate the accuracy of ages obtained using the AAR technique. The 35 goats were divided into three datasets: all goats (n = 35), goats >0.5 yrs old (n = 26) and goats >2 yrs old (n = 19). Leave-one-out analyses were performed on the three sets of data. Normalized root mean squared errors for the group of goats >0.5 yrs old were found to be the smallest. The higher variation in D/L measurements found for young goats <0.5 yrs can probably be explained by a period of continued postnatal growth of the eye lens. Normalized root mean squared errors from the leave-one-out cross-validation analyses based on goats >0.5 yrs old was for three age groups of the goats: 0.934 yrs for young goats <2 yrs (n = 16), 0.102 yrs for adult goats from 2–8 yrs (n = 15) and 0.133 yrs for old goats >8 yrs (n = 4). Thus, the age of an adult or an old animal can be predicted with approximately 10% accuracy, whereas the age of a young animal is difficult to predict. A goat specific racemization rate, as a 2kAsp value, was estimated to 0.0107 ± 3.8 x 10-4 SE (n = 26). The 2kAsp values from 12 species, four estimated in this study and another eight published, were used to examine the effect of core body temperature on the rate of racemization. A positive relationship between AAR and temperature was found (r2 = 0.321) but results also suggest that other factors besides temperature are involved in the racemization process in living animals. Based on our results we emphasize that non-species-specific racemization rates should be used with care in AAR age estimation studies and that the period of postnatal growth of the eye lens be considered when estimating species-specific D/L0 values and ages of young individuals.

Disability in progressive MS is associated with T2 lesion changes

BACKGROUND

Progressive multiple sclerosis (MS) is characterised by diffuse changes on brain magnetic resonance imaging (MRI), which complicates the use of MRI as a diagnostic and prognostic marker. The relationship between MRI measures (conventional and non-conventional) and clinical disability in progressive MS therefore warrants further investigation.

OBJECTIVE

To investigate the relationship between clinical disability and MRI measures in patients with progressive MS.

METHODS

Data from 93 primary and secondary progressive MS patients who had participated in 3 phase 2 clinical trials were included in this cross-sectional study. From 3T MRI baseline scans we calculated total T2 lesion volume and analysed magnetisation transfer ratio (MTR) and the diffusion tensor imaging indices fractional anisotropy (FA) and mean diffusivity (MD) in T2 lesions, normal-appearing white matter (NAWM) and cortical grey matter. Disability was assessed by the Expanded Disability Status Scale (EDSS) and the MS functional composite.

RESULTS

T2 lesion volume was associated with impairment by all clinical measures. MD and MTR in T2 lesions were significantly related to disability, and lower FA values correlated with worse hand function in NAWM. In multivariable analyses, increasing clinical disability was independently correlated with increasing T2 lesion volumes and MTR in T2 lesions.

CONCLUSION

In progressive MS, clinical disability is related to lesion volume and microstructure.

Spinal cord atrophy in anterior-posterior direction reflects impairment in multiple sclerosis

OBJECTIVE

To investigate how atrophy is distributed over the cross section of the upper cervical spinal cord and how this relates to functional impairment in multiple sclerosis (MS).

METHODS

We analysed the structural brain MRI scans of 54 patients with relapsing-remitting MS (n=22), primary progressive MS (n=9), secondary progressive MS (n=23) and 23 age- and sex-matched healthy controls. We measured the cross-sectional area (CSA), left-right width (LRW) and anterior-posterior width (APW) of the spinal cord at the segmental level C2. We tested for a nonparametric linear relationship between these atrophy measures and clinical impairments as reflected by the Expanded Disability Status Scale (EDSS) and Multiple Sclerosis Impairment Scale (MSIS).

RESULTS

In patients with MS, CSA and APW but not LRW were reduced compared to healthy controls (P<.02) and showed significant correlations with EDSS, MSIS and specific MSIS subscores.

CONCLUSION

In patients with MS, atrophy of the upper cervical cord is most evident in the antero-posterior direction. As APW of the cervical cord can be readily derived from standard structural MRI of the brain, APW constitutes a clinically useful neuroimaging marker of disease-related neurodegeneration in MS.

Trichuris suis ova therapy in relapsing multiple sclerosis is safe but without signals of beneficial effect

Background:

An observational study has suggested that relapsing–remitting multiple sclerosis patients with helminth infections have lower disease activity and progression than uninfected multiple sclerosis patients.

Objective:

To evaluate the safety and efficacy on MRI activity of treatment with TSO in relapsing MS.

Methods:

The study was an open-label, magnetic resonance imaging assessor-blinded, baseline-to-treatment study including ten patients with relapsing forms of multiple sclerosis. Median (range) age was 41 (24–55) years, disease duration 9 (4–34) years, Expanded Disability Status Scale score 2.5 (1–5.0), and number of relapses within the last two years 3 (2–5). Four patients received no disease modifying therapy, while six patients received IFN-β. After an observational period of 8 weeks, patients received 2500 ova from the helminth Trichuris suis orally every second week for 12 weeks. Patients were followed with serial magnetic resonance imaging, neurological examinations, laboratory safety tests and expression of immunological biomarker genes.

Results:

Treatment with Trichuris suis orally was well-tolerated apart from some gastrointestinal symptoms. Magnetic resonance imaging revealed 6 new or enlarged T2 lesions in the run-in period, 7 lesions in the early period and 21 lesions in the late treatment period. Two patients suffered a relapse before treatment and two during treatment. Eight patients developed eosinophilia. The expression of cytokines and transcription factors did not change.

Conclusions:

In a small group of relapsing multiple sclerosis patients, Trichuris suis oral therapy was well tolerated but without beneficial effect.

Application of the PredictAD decision support tool to a Danish cohort of patients with Alzheimer's disease and other dementias

BACKGROUND

The diagnosis of Alzheimer's disease (AD) is based on an ever-increasing body of data and knowledge making it a complex task. The PredictAD tool integrates heterogeneous patient data using an interactive user interface to provide decision support. The aim of this project was to investigate the performance of the tool in distinguishing AD from non-AD dementia using a realistic clinical dataset.

METHODS

We retrieved clinical data from a group of patients diagnosed with AD (n = 72), vascular dementia (VaD, n = 30), frontotemporal dementia (FTD, n = 25) or dementia with Lewy bodies (DLB, n = 14) at the Copenhagen Memory Clinic at Rigshospitalet. Three classification methods were applied to the data in order to differentiate between AD and a group of non-AD dementias. The methods were the PredictAD tool's Disease State Index (DSI), the naïve Bayesian classifier and the random forest.

RESULTS

The DSI performed best for this realistic dataset with an accuracy of 76.6% compared to the accuracies for the naïve Bayesian classifier and random forest of 67.4 and 66.7%, respectively. Furthermore, the DSI differentiated between the four diagnostic groups with a p value of <0.0001.

CONCLUSION

In this dataset, the DSI method used by the PredictAD tool showed a superior performance for the differentiation between patients with AD and those with other dementias. However, the methods need to be refined further in order to optimize the differential diagnosis between AD, FTD, VaD and DLB.

Changes in blood testosterone concentrations after surgical and chemical sterilization of male free-roaming dogs in southern Chile

There is a growing interest in chemical sterilization as an alternative to surgical castration in large-scale sterilization campaigns to control canine populations. An important step toward understanding the short-term and long-term effects of chemical sterilants is to determine their impact on blood testosterone concentrations, particularly as these could influence dog behavior after treatment. A field trial was conducted with 118 free-roaming male dogs in the Chilean Patagonia, where 36 dogs were chemically sterilized using EsterilSol, 39 dogs were surgically castrated, and 43 dogs remained intact as controls. Blood testosterone levels were determined at four time periods: on enrollment 6 months before treatment (t-6m), at the time of treatment (t0, within one hour after surgical castration or chemical sterilization and during a concurrent 2-week period for the control group), four (t+4m), and six (t+6m) months after treatment. Intrinsic and temporal factors were evaluated; age was significantly associated with testosterone, where dogs 2- to 4-year-old had the highest testosterone concentrations (P = 0.036), whereas body weight and body condition scores were not associated with testosterone; testosterone concentration was not influenced by time of day, month, or season. After treatment (t+4m and t+6m), all of the surgically castrated dogs had testosterone concentrations below 1.0 ng/mL. On the basis of this cut point (<1 ng/mL), testosterone remained unchanged in 66% of the chemically sterilized dogs at both t+4m and t+6m; it remained low for 22% of dogs at both t+4m and t+6m; it was unchanged at t+4m but low at t+6m in 9% of dogs; and, it was low at t+4m but reverted back to unchanged at t+6m in one dog (3%). Incidentally, testosterone in chemically sterilized dogs increased dramatically within 1 hour of treatment (t0), more than doubling (131%) the concentration of control dogs at the time of treatment (t0), likely because of severe necrosis of interstitial cells. The use of EsterilSol as a method of sterilizing dogs had a variable effect on blood testosterone concentrations. Approximately, 30% of chemically sterilized dogs had a reduced testosterone concentration (actual maximum, 1 ng/mL) after 6 months, similar to that of surgically castrated dogs. Most chemically sterilized dogs, however, showed no long-term changes in blood testosterone concentrations.

Necrosuppurative orchitis and scrotal necrotizing dermatitis following intratesticular administration of zinc gluconate neutralized with arginine (EsterilSol) in 2 mixed-breed dogs

Intratesticular injection of EsterilSol (zinc gluconate neutralized with arginine) is a chemical sterilant for male dogs sometimes used in population control campaigns. Adverse reactions have been reported in 1% to 4% of treated dogs, but detailed histomorphologic descriptions are lacking. During a behavioral study conducted in the Chilean Patagonia in 2012, severe necrosuppurative orchitis and ulcerative dermatitis were observed in 2 of 36 (6%) dogs sterilized with EsterilSol according to the manufacturer's instructions. Reactions were noted on days 8 and 7 postinjection and required scrotal ablation on days 8 and 13, respectively; neither reaction was associated with the injection site. Although self-trauma following administration may have contributed, the cause of the adverse reactions is uncertain. EsterilSol is a relatively uncomplicated method to sterilize male dogs, but the occurrence of severe adverse reactions several days after administration emphasizes the need for the provision of long-term monitoring and veterinary care during sterilization campaigns using this product.

The apolipoprotein E epsilon4-allele and antihypertensive treatment are associated with increased risk of cerebral MRI white matter hyperintensities

OBJECTIVE

Apolipoprotein E-epsilon4 (APOE-epsilon4) is a potential risk factor for cerebral vascular disease. The aim of the present study was to examine the relative importance of APOE-epsilon4 and other relevant risk factors for the extent of cerebral white matter hyperintensity (WMH) in a community-based sample of elderly subjects.

MATERIALS AND METHODS

From a cohort of 976 subjects born in 1914, APOE genotype was determined and MRI examinations were carried out in 75 subjects. WMH were rated using a standard semi-quantitative method. ANOVA and regression analyses were conducted to explore the relative importance of the potential risk factors.

RESULTS

APOE genotype and antihypertensive treatment were significantly associated with severity of total WMH load (P < 0.05).

CONCLUSIONS

The study confirmed the association between APOE-epsilon4 and WMH. Pharmaceutical treatment for arterial hypertension was also associated with the total burden of WMH in this study.

A pulse-rate dependence of dose per monitor unit and its significant effect on wedged-shaped fields delivered with variable dose rate and a moving jaw

Wedge-shaped dose distributions are delivered on some modern linear accelerators with a virtual wedge, combining variable dose rate and a moving jaw. Drift in the wedge factor and wedge angle of a 20 X 20 cm field for the 60 degree virtual wedge was found commonplace in several models of linear accelerator from one manufacturer. It was found that errors in dose delivery both on and off axis could exceed 5% if quality assurance checks are limited to 10 X 10 cm or smaller fields or wedge angles of 45 degrees or less. A procedure to easily identify and remedy the problem is presented. In each case the change was due to variation in dose per monitor unit (D/MU) with the electron beam pulse rate. The variation was traced to a pair of circuit boards in the dosimetry system, one for each output measurement channel. Wedge factors and dose profiles measured before and after board replacement on 4 accelerators, and for a set of defective boards placed on one of the accelerators, were compared. The effect was largest for the wedge with the steepest profile (60 degree wedge angle) and the largest field measured: 20 X 20 cm. In this case, a 1% variation in D/MU with a factor of 5 reduction in pulse rate corresponded to an average 0.8% change in wedge factor and 0.8% change in the off axis ratio at 8.5 cm off axis on the high dose side of the wedge field, 0.3% on the low dose side. After board replacement, wedge factors and profiles measured on the 4 machines generally agreed to 2% for the full range of wedge angles and field sizes. Quality assurance of virtual wedges is discussed in light of the new findings.

Decline in intelligence is associated with progression in white matter hyperintensity volume

OBJECTIVES

To quantify the time course of white matter hyperintensities (WMH) and assess the association between progression and cognitive decline in non-demented octogenarians.

METHODS

From a Danish cohort of 698 people born in 1914, 26 participated in neuropsychological assessment (Wechsler adult intelligence scale) initiated at age 50, including cognitive testing and cerebral magnetic resonance imaging at the 80 and 85 year studies. WMH volumes were quantified and partial correlations were calculated between WMH volume change and decline in WAIS scores from 80 to 85.

RESULTS

Progression in WMH volume ranged from 0 ml to 20.7 ml, providing a median increase of 2.6 ml (range 0.1 to 20.7, p<0.001) and, with a mean time interval between scans of 3.8 years, a rate of progression of 0.63 (0 to 6.8) ml/year. WMH volume measures for the two hemispheres were highly correlated (r = 0.95) and did not differ significantly. Increase in WMH volume was correlated with a simultaneous decline in verbal IQ (r = -0.65, p = 0.001), while baseline WMH was associated with subsequent decline in performance subtests (digit symbol, r = -0.57, p = 0.02).

CONCLUSIONS

The association between WMH and decline in essential cognitive abilities even in well preserved elderly people suggests that WMH should be regarded as a risk factor for cognitive impairment and dementia.

Cerebral perfusion and cerebrovascular reactivity are reduced in white matter hyperintensities

BACKGROUND AND PURPOSE

There is growing evidence that white matter hyperintensities (WMH) should not be considered as benign age-dependent changes on MR images but indicate pathological changes with clinical consequences. Previous studies comparing subjects with WMH to normal controls have reported global reductions in cerebral blood flow (CBF) and cerebral vascular reactivity. In this study, we examined localized hemodynamic status to compare WMH to normal appearing white matter (NAWM).

METHODS

A group of 21 normal 85-year-old subjects were studied using dynamic contrast-enhanced MRI together with administration of acetazolamide. From a combination of anatomic images with different signal weighting, regions of interest were generated corresponding to gray and white matter and WMH. Localized measurements of CBF and cerebral blood volume (CBV) and mean transit time were obtained directly within WMH and NAWM.

RESULTS

When comparing WMH to NAWM, measurements showed significantly lower CBF (P=0.004) and longer mean transit time (P< 0.001) in WMH but no significant difference in CBV (P=0.846). The increases in CBF and CBV induced by acetazolamide were significantly smaller in WMH than in NAWM (P=0.026, P<0.001).

CONCLUSION

These results show that a change in the hemodynamic status is present within the WMH, making these areas more likely to be exposed to transient ischemia inducing myelin rarefaction. In the future, MRI may be used to examine the effect of therapeutic strategies designed to prevent or normalize vascular changes.

Cerebral hemodynamic changes measured by gradient-echo or spin-echo bolus tracking and its correlation to changes in ICA blood flow measured by phase-mapping MRI

Changes in cerebral blood flow (CBF) induced by Acetazolamide (ACZ) were measured using dynamic susceptibility contrast MRI (DSC-MRI) with both spin echo (SE) EPI and gradient echo (GE) EPI, and related to changes in internal carotid artery (ICA) flow measured by phase-mapping. Also examined was the effect of repeated bolus injections. CBF, cerebral blood volume (CBV), and mean transit time (MTT) were calculated by singular value decomposition (SVD) and by deconvolution using an exponential function as kernel. The results showed no dependency on calculation method. GE-EPI measured a significant increase in CBF and CBV in response to ACZ, while SE-EPI measured a significant increase in CBV and MTT. CBV and MTT change measured by SE-EPI was sensitive to previous bolus injections. There was a significant linear relation between change in CBF measured by GE-EPI and change in ICA flow. In conclusion, GE-EPI under the present condition was superior to SE-EPI in monitoring cerebral vascular changes.

Relation between age-related decline in intelligence and cerebral white-matter hyperintensities in healthy octogenarians: a longitudinal study

BACKGROUND

White-matter hyperintensities are commonly found on magnetic resonance imaging (MRI) of elderly people with or without dementia. Studies of the relation between severity of white-matter hyperintensities and cognitive impairment have had conflicting results. We undertook a longitudinal study of age-related decline in intellectual function and MRI at age 80 years.

METHODS

From a cohort of 698 people born in 1914 and living in seven municipalities in Denmark, 68 healthy non-demented individuals had been tested with the Wechsler adult intelligence scale (WAIS) at ages 50, 60, and 70, and they agreed to further WAIS testing at age 80, and cerebral MRI at age 80-82 (mean age 82.3 years). We scored separately the numbers of periventricular and deep white-matter hyperintensities.

FINDINGS

Scores for periventricular hyperintensities in this sample included all possible degrees of severity, but no participant scored more than 75% of maximum for deep white-matter hyperintensities. Neither type was related to the WAIS IQs of the 80-year assessment, but both were significantly associated with decline in performance IQ from age 50 to age 80 years (bivariate correlation coefficients 0.32, p=0.0087, and 0.28, p=0.0227, respectively). An analysis based on two WAIS subtests showed that the association between white-matter hyperintensities and cognitive impairment was significant only for cognitive decline in the decade 70-80 years.

INTERPRETATION

Both periventricular and deep white-matter hyperintensities are related to decline in intelligence but, in healthy octogenarians, the cumulative effect of these features alone explains only a small part of the large differences among individuals in age-related decline in intelligence. Interpretation of the presence and severity of white-matter hyperintensities in a diagnostic context must be done cautiously.

Central nervous system resuscitation

Traumatic injury to the central nervous system induces delayed neuronal death, which may be mediated by acute and chronic neurochemical changes. Experimental identification of these injury mechanisms and elucidation of the neurochemical cascade following trauma may provide enhanced opportunities for treatment with novel neuroprotective strategies.

Regulation of PAF-induced platelet responses by cyclic nucleotides

The existence of cross-talk mechanisms between the cyclic nucleotide system and other transduction systems involved in PAF-activated platelets is described in this study. A protein of 125 kDa, identified as pp 125(FAK), is tyrosine phosphorylated by PAF in a time- and concentration-dependent manner. The presence of a cAMP- or a cGMP-elevating agent, used alone or in combination, together with PAF diminished tyrosine phosphorylation. The sensitivity to cAMP shown by PAF-induced ppl25 phosphorylation on tyrosine residues was similar to PAF-induced phosphorylation of a 47-kDa protein (pp47) on serine and threonine. In contrast, the latter was not affected in the presence of a cGMP-elevating agent, although it was able to enhance synergistically the inhibitory effect of forskolin. Data reported herein also show that pp47 phosphorylation and serotonin secretion are not closely correlated. Accordingly, sodium nitroprusside (SNP) did not have any effect on phosphorylation of pp47, but it was able to inhibit serotonin secretion when added alone, and it showed a synergistic inhibitory action with forskolin.

Therapeutic approaches for the prevention of secondary brain injury

The precise mechanisms underlying secondary brain damage after traumatic injury to the central nervous system (CNS) are not well understood, and delayed neuronal injury may result from pathological changes in neurotransmitter release, synthesis or generation of endogenous autodestructive neurochemicals and/ or inflammatory mediators, or alterations in endogenous protective or trophic factors. Recent identification of such factors and the elucidation of the timing of the neurochemical cascade following CNS injury provides a window of opportunity for therapeutic intervention with pharmacological compounds which modify synthesis, release, receptor binding or physiological activity of neurotoxic factors. A number of recent experimental studies have reported that pharmacological modification of the post-traumatic neurochemical milieu can promote functional recovery in a variety of animal models of CNS trauma. This paper summarizes recent work suggesting that pharmacological manipulation of several key neurotransmitter and neurochemical systems can attenuate neuronal damage and improve functional outcome associated with traumatic brain injury.

PCA-4248, a PAF receptor antagonist, inhibits PAF-induced phosphoinositide turnover

The effect of a new PAF (platelet activating factor; 1-O-alkyl-2-acetyl-sn-glycero-3-phosphoryl-choline) receptor antagonist, PCA-4248 (2-phenylthio)ethyl-5-metoxycarbonyl-2,4,6-trimethyl-1, 4-dihydropyridine-3-carboxylate), on phosphoinositide turnover evoked by PAF was investigated. PAF treatment resulted in an increased 32P incorporation into phosphoinositides and phosphatidic acid in rabbit platelets. Treatment with PCA-4248 abolished both effects in a dose-dependent manner, 10 microM being the most effective dose. In thrombin stimulated platelets, phosphoinositide turnover was not influenced by PCA-4248. In addition, PAF caused a rapid and significant increase in protein phosphorylation. Thus, PAF treatment resulted in a marked phosphorylation of two proteins of 47 kDa and 20 kDa. Treatment with PCA-4248 resulted in an inhibition of these actions. Serotonin secretion evoked by PAF was also inhibited by PCA-4248. It is concluded that PCA-4248 antagonizes the PAF effects by acting as a competitive antagonist at the PAF receptor level as evidenced from binding studies.

[Apoplexy with rapidly deteriorating symptoms--"stroke in progression". Hemodynamic and clinical aspects]

Stroke-in-progression, SIP, occurs in about 30% of patients with acute stroke and negatively affects the prognosis and mortality. The underlying caused are thought to be clot propagation, cerebral haemorrhage or oedema. In some cases these rather obvious mechanisms cannot be demonstrated, and other variables such as a decrease in blood pressure must be considered as major factors. In this paper the basic haemodynamic mechanisms of cerebral blood flow and the relevant pathophysiology of focal cerebral infarcts are described with emphasis on the penumbra. In addition, available clinical studies are reviewed and current treatment discussed. Our main conclusion is that to assure sufficient collateral flow a high perfusion pressure must be maintained, and we advocate withholding antihypertensive therapy during the acute phase of focal cerebral ischaemia.

[Treatment of high blood pressure in patients with acute apoplexy]

The study was performed to investigate how often reduction of high blood pressure (> or = 220 mmHg systolic and or > or = 120 mmHg diastolic) was attempted in patients with acute stroke or transient ischemic attacks (TIA). Of 1351 consecutive patients with acute stroke or TIA 119 had high blood pressure on admission. In 15 patients the stroke was so severe that treatment was not considered. In the remaining 104 patients reduction of the blood pressure was attempted in 28 (27%); in 23 patients immediately following admission. None of the patients had symptoms or signs of hypertensive encephalopathy. It is concluded that reduction of high blood pressure in patients with stroke or TIA is attempted too often. As autoregulation is commonly impaired in acute stroke, reduction of systemic blood pressure may enhance ischaemic tissue damage. Reduction of blood pressure in acute stroke should be considered only in case of hypertensive encephalopathy.

[Reducing hypertension may worsen symptoms of acute apoplexy]

Patients with acute stroke often present with high blood pressure (BP) on hospital admission. Because hypertension is a risk factor for stroke, and because severe BP elevation may increase oedema and the risk of haemorrhage, acute antihypertensive therapy might seem reasonable. On the other hand, the increase in BP in the acute stage might be considered a beneficial pathophysiological response maintaining the perfusion pressure to the ischaemic area and, in particular, the surrounding penumbra. As illustrated in the case presented here, lowering the BP in the early stage may be associated with progression of neurological deficits, very likely due to a reduction of perfusion to the penumbra thus enlarging the infarct.

8-methoxypsoralen increases daytime plasma melatonin levels in humans through inhibition of metabolism

It is well established that in healthy humans oral intake of 5- or 8-methoxypsoralen (5- and 8-MOP) is followed by a significant increase in plasma melatonin concentrations. The effect of psoralen on rat melatonin has been studied in vitro and in vivo and a stimulation of release or secretion from the pineal gland has been suggested. In this study we examined the time-related changes in plasma concentrations of 8-MOP, melatonin and 6-sulfatoxymelatonin in 15 patients admitted for routine psoralen plus UVA therapy. On the first day of treatment blood samples were collected before, and 30, 60, 66 and 90 min after intake of 8-MOP (0.6 mg/kg). Although the rate of 8-MOP absorption varied greatly, a significant increase (P = 0.0002) in melatonin levels was found 60 min after 8-MOP intake. During UVA exposure a strongly correlated decrease in mean melatonin and mean 8-MOP concentrations was found, indicating an effect of UVA radiation, either direct or 8-MOP mediated, on circulating melatonin levels. Plasma 6-sulfatoxymelatonin concentrations decreased significantly between all time points, suggesting inhibition of melatonin metabolism.

Dissociation between secretion and protein phosphorylation in agonist-stimulated platelets; action of PCA-4230, a new antithrombotic drug

We have studied the effects of PCA-4230, a new dihydropyridine derivative with antithrombotic activity, on the secretion of dense and alpha-granules from platelets and on the protein phosphorylation in platelets after stimulation by agonists. The drug prevented both dense and alpha-granule secretion evoked by thrombin, platelet-activating factor (PAF) and ionophore A23187, the former secretion being more sensitive than the latter one to the PCA-4230 action. These inhibitory effects on secretion processes did not correlate with the differential action of PCA-4230 on protein phosphorylation. Thus, the 40 kDa protein phosphorylation evoked by thrombin was potentiated whereas that elicited by ionophore A23187 was partially inhibited. The 20 kDa protein phosphorylation was practically insensitive to the drug action. These data, together with previous evidence reported by us on PCA-4230, lead us to suggest the existence of a common and critical step for platelet secretion evoked by agonists with different signal transduction pathways.

Sudden natural death in childhood. A review of forensic autopsy protocols in cases of sudden death between the ages of one and five years, 1982-1991, with a special view to sudden unexplained death

All cases of sudden death of individuals between the ages of one and five years examined at the Forensic Institute, Copenhagen, in a 10-year period were identified to assess the impact of sudden unexplained death in this age group. Of a total of 68 cases, 27 cases were due to accidents, there were 13 cases of homicide, 27 cases were sudden natural deaths and in 1 case the manner of death was uncertain. The autopsy records and histological sections in the 27 cases of natural death were reviewed; the cause of death was not explained in 11 of these cases (40%). Seven cases were previously considered to be caused by infectious disease or aspiration. Criteria for classification are discussed.

Platelet-activating factor stimulates protein kinase C translocation in cerebral microvessels

The effects of platelet-activating factor (PAF) on distribution of protein kinase C activity in brain microvessels have been examined. Our results indicate that PAF caused an increase of protein kinase C activity in membrane, accompanied by a loss of activity in the cytosol. This effect resulted to be dose-dependent and the translocation was evident after 30 min of PAF treatment. These results suggest that PAF could play a role in transport processes in the blood-brain barrier, involving protein phosphorylation by activation of protein kinase C.

PAF and thrombin actions in platelets are selectively affected by a new 1,4-dihydropyridine derivative

In the present study we described the effects of a new 1,4-dihydropyridine derivative with antithrombotic activity on phosphoinositide turnover in washed platelets stimulated by either platelet-activating factor or thrombin. In 32P-labeled rabbit platelets, both PAF and thrombin evoked a transient loss of [32P]phosphatidylinositol 4,5-bisphosphate (PIP2) and, thereafter, labeling increased over the control value. Concomitantly, a progressive formation of phosphatidic acid was observed. In [3H]arachidonate labeled platelets, both agonists elicited an increase in diacylglycerol (DAG) levels and arachidonate release. Pretreatment of platelets with the new dihydropyridine derivative (PCA-4230) prevents, in a dose-dependent fashion, the PAF-evoked variations in phosphoinositide turnover and DAG production. However, thrombin-induced variations were rather enhanced by PCA-4230. With respect to arachidonate release and platelet aggregation, the drug was again selective against PAF and thrombin. Although PCA-4230 shows some PAF antagonistic activity, its effects on PAF-evoked responses did not seem only due to an antagonism at receptor level. In view of the present results, the drug is not only able to discern the pathways of platelet activation by which PAF and thrombin exert their action, but it also affects selectively the enhanced phosphoinositide turnover and arachidonate release evoked by thrombin. Thereafter, PCA-4230 is a suitable tool to explore the mechanisms of action of the natural agonists.