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Biomedical subjects

D Ebert

Publications and source records attributed to D Ebert.

At least 37 records · Page 2Linked to original sources
PubMed2002

Amygdala pathology in psychosis of epilepsy: A magnetic resonance imaging study in patients with temporal lobe epilepsy.

Psychosis of epilepsy (POE) has been recognized as a severe complication of chronic intractable epilepsy for more than a century. Most of the clinical symptoms of POE are reminiscent of schizophrenia. Nevertheless, there is general agreement that the phenomenology of POE differs from classical schizophrenia. The temporal lobe hypothesis of schizophrenia put forward in the 1960s notes that episodes with paranoid psychoses are more prevalent in temporal lobe epilepsy (TLE). However, the aetiology and pathogenesis of POE are poorly understood. One of the strongest biological findings in schizophrenia is volume loss of temporal lobe structures and the hippocampus in particular. In order to test the hypothesis that atrophy of the hippocampus and the amygdala is found in patients with TLE and POE, we performed a retrospective study of all patients with TLE who were admitted to the assessment unit of the Chalfont Centre for Epilepsy from 1995 until 1999. Twenty-six (2.6%) of these 1008 patients fulfilled inclusion criteria and were compared with 24 patients with TLE without psychopathology and 20 healthy volunteers. All patients underwent extensive MRI investigations, including volumetric data sets and quantitative T(2 )relaxometry. We found that patients with TLE and POE differed from patients with TLE alone and healthy volunteers in that the total brain volumes were significantly smaller. While there were no differences in hippocampal volumes between the three study groups, there was a significant 16-18% enlargement of the amygdala on both sides in patients with POE. Our findings support the notion that POE is a distinct nosologic entity differing from schizophrenia not only in clinical details but also in neurobiological aspects. The finding of amygdala enlargement agrees with the observation of an association between dysphoric disorders of epilepsy and POE described nearly 100 years ago.

Amygdala↗
PubMed2001

Attention-deficit disorder in adults with or without hyperactivity: where is the difference? A study in humans using short echo (1)H-magnetic resonance spectroscopy.

The DSM-IV distinguishes three subtypes of attention deficit hyperactivity disorder: The predominantly inattentive subtype (ADD), the hyperactive-impulsive subtype (ADHD) and the combined subtype. We used short echo time (1)H-magnetic resonance spectroscopy (TE=30 ms, TR=3000 ms) for absolute quantification of neurometabolites using the LC model algorithm to investigate a possible metabolic neuropathology in adult patients with ADD and ADHD and compared their spectra with healthy controls (n=5 in each group). Spectra were acquired in the left dorsolateral prefrontal cortex and the left striatum. There was a significant group difference in N-acetylaspartate (NAA) concentration in the left dorsolateral prefrontal cortex distinguishing patients with the ADHD from patients with pure ADD and healthy controls. The absolute NAA concentration was significantly reduced only in the ADHD group. Since NAA-depletion reflects a state of neuronal dysfunction, this finding indicates evidence of subtle left prefrontal neuropathology in ADHD in adults.

Adult↗
PubMed2001

Urinary oxalate excretion in female calcium oxalate stone formers with and without a history of recurrent urinary tract infections.

Therapy with antibiotics in recurrent urinary tract infections may destroy colonies of Oxalobacter formigenes in the intestinal tract. A lack of oxalate degradation caused by the absence of this bacterium is suggested to contribute to the hyperabsorption of dietary oxalate and to the increase in urinary oxalate excretion. The present study was performed to evaluate the effect of recurrent urinary tract infections and subsequent changes induced in the urinary excretion profile in female calcium oxalate stone formers. Serum biochemical profiles, 24-h urinary parameters, and the personal characteristics of 57 female calcium oxalate stone patients with recurrent urinary tract infections (RUTI) were compared with 78 female calcium oxalate stone patients without a history of urinary tract infection. All subjects were recruited during the same period. In female patients with RUTI, urinary oxalate excretion was significantly higher (0.374 mmol/day) than in females without urinary tract infection (0.308 mmol/day) (P < 0.05). Moreover, the mean 24-h pH value and urinary sodium excretion were significantly higher in women with RUTI than in women without a history of urinary tract infection. The significantly higher urinary oxalate excretion in female calcium oxalate stone formers with recurrent urinary tract infections may be associated with the application of antibiotics and a subsequent temporary or permanent decolonization of Oxalobacter formigenes.

Adult↗
PubMed2001

Evolution in health and disease: work in progress.

This article surveys progress in Darwinian medicine since 1991. Evolutionary thinking has been providing an increasing flow of fresh ideas into medical science, ideas that would not be suggested by other perspectives. Recent contributions have shed new light on the evolution of virulence, of antibiotic resistance, of oocytic atresia, of menopause, of the timing of the expression of genetic disease, of links between mate choice and disease resistance, and of genomic conflict between mother and fetus over resource provisioning. An important consequence of changes from the environment of evolutionary adaptedness concerns reproductive cancers; the incidence of reproductive cancers may be linked to changes in the frequency of menstruation in postindustrial societies. Other intriguing developments include some unanticipated and undesirable consequences of good hygiene, hope from an unexpected quarter for progress on nerve and muscle regeneration, evolutionary interpretations of mental disease, and insights from functional genomics into the nature of tradeoffs. The application of evolutionary thinking to problems in medical research and practice has thus yielded an abundant and growing harvest of insights. Some are well founded, others remain speculative. The field is moving from an initial phase dominated by speculation and hypothesis formation into a more rigorous phase of experimental testing of explicit alternatives. Currently the most promising areas, those in which experimental rigor can be applied efficiently, include experimental evolution and functional genomics. The pioneers can be proud of what they have set in motion.

Adaptation, Physiological↗
PubMed2001

Genetic variation in a host-parasite association: potential for coevolution and frequency-dependent selection.

Models of host-parasite coevolution assume the presence of genetic variation for host resistance and parasite infectivity, as well as genotype-specific interactions. We used the freshwater crustacean Daphnia magna and its bacterial microparasite Pasteuria ramosa to study genetic variation for host susceptibility and parasite infectivity within each of two populations. We sought to answer the following questions: Do host clones differ in their susceptibility to parasite isolates? Do parasite isolates differ in their ability to infect different host clones? Are there host clone-parasite isolate interactions? The analysis revealed considerable variation in both host resistance and parasite infectivity. There were significant host clone-parasite isolate interactions, such that there was no single host clone that was superior to all other clones in the resistance to every parasite isolate. Likewise, there was no parasite isolate that was superior to all other isolates in infectivity to every host clone. This form of host clone-parasite isolate interaction indicates the potential for coevolution based on frequency-dependent selection. Infection success of original host clone-parasite isolate combinations (i.e., those combinations that were isolated together) was significantly higher than infection success of novel host clone-parasite isolate combinations (i.e., those combinations that were created in the laboratory). This finding is consistent with the idea that parasites track specific host genotypes under natural conditions. In addition, correspondence analysis revealed that some host clones, although distinguishable with neutral genetic markers, were susceptible to the same set of parasite isolates and thus probably shared resistance genes.

Animals↗
PubMed2001

Temporal patterns of genetic variation for resistance and infectivity in a Daphnia-microparasite system.

Theoretical studies have indicated that the population genetics of host-parasite interactions may be highly dynamic. with parasites perpetually adapting to common host genotypes and hosts evolving resistance to common parasite genotypes. The present study examined temporal variation in resistance of hosts and infectivity of parasites within three populations of Daphnia magna infected with the sterilizing bacterium Pasteuria ramosa. Parasite isolates and host clones were collected in each of two years (1997, 1998) from one population; in two other populations, hosts were collected from both years, but parasites from only the first year. We then performed infection experiments (separately for each population) that exposed hosts to parasites from the same year or made combinations involving hosts and parasites from different years. In two populations, patterns were consistent with the evolution of host resistance: either infectivity or the speed with which parasites sterilized hosts declined from 1997 to 1998. In another population, infectivity, virulence, and parasite spore production did not vary among host-year or parasite-year. For this population, we also detected strong within-population genetic variation for resistance. Thus, in this case, genetic variability for fitness-related traits apparently did not translate into evolutionary change. We discuss a number of reasons why genetic change may not occur as expected in parasite-host systems, including negative correlations between resistance and other traits, gene flow, or that the dynamic process itself may obscure the detection of gene frequency changes.

Animals↗
PubMed2001

Antidepressive response to sleep deprivation in unipolar depression is not associated with dopamine D3 receptor genotype.

The psychostimulant theory of antidepressive sleep deprivation (SD) proposes a contribution of dopamine D3 receptors (DRD3) in the limbic system to the antidepressant effects of SD. Neuroendocrinological studies suggest a positive correlation of clinical response to SD and cortisol secretion. We hypothesized that the clinical response to SD and amount of cortisol secretion upon SD is associated with the 1-1 genotype of the Bal1 polymorphism of DRD3 on exon 1. In this study, aiming at evaluating the feasibility of screening large patient samples, 52 inpatients (19 males/33 females) with unipolar depression and a score of 18 or more on the 21-item Hamilton Depression Rating Scale were treated with 1 night of total SD. We found that 31% of our patients responded to SD. There was no association between response to SD and the genotype of the DRD3 Bal1 polymorphism (p < 0.879). There was also no association between increase in cortisol secretion after SD and DRD3 genotypes (p < 1.000) in a subgroup of patients. Statistical power analysis ruled out a major effect of the DRD3 Bal1 polymorphism on clinical response to SD. These results suggest that the DRD3 Bal1 polymorphism is not a promising lead to be followed up in larger patient samples.

Adult↗
PubMed2000

The cause of parasitic infection in natural populations of Daphnia (Crustacea: Cladocera): the role of host genetics.

Disease patterns in nature may be determined by genetic variation for resistance or by factors, genetic or environmental, which influence the host-parasite encounter rate. Elucidating the cause of natural infection patterns has been a major pursuit of parasitologists, but it also matters for evolutionary biologists because host resistance genes must influence the expression of disease if parasite-mediated selection is to occur. We used a model system in order to disentangle the strict genetic component from other causes of infection in the wild. Using the crustacean Daphnia magna and its sterilizing bacterial parasite Pasteuria ramosa, we tested whether genetic variation for resistance, as determined under controlled conditions, accounted for the distribution of infections within natural populations. Specifically, we compared whether the clonally produced great-granddaughters of those individuals that were infected in field samples (but were subsequently 'cured' with antibiotics) were more susceptible than were the great-granddaughters of those individuals that were healthy in field samples. High doses of parasite spores led to increased infection in all four study populations, indicating the importance of encounter rate. Host genetics appeared to be irrelevant to natural infection patterns in one population. However, in three other populations hosts that were healthy in the field had greater genetic-based resistance than hosts that were infected in the field, unambiguously showing the effect of host genetic factors on the expression of disease in the wild.

Animals↗
PubMed2000

Prefrontal cortical hypometabolism during low-dose interferon alpha treatment.

OBJECTIVE: To evaluate prospectively interferon alpha (IFN-alpha) associated effects on cerebral glucose metabolism and its correlation to neuropsychiatric symptoms during low-dose IFN-alpha-treatment. METHODS: Eleven patients treated with low-dose IFN-alpha for chronic hepatitis C were prospectively evaluated by neuropsychiatric tests and cerebral [18F]deoxyglucose positron emission tomography (FDG-PET) before and in the 12th week of treatment. PET images were spatially normalized, corrected for variance in global activity and pixel-based t-statistics were calculated for each set of PET scans using SPM96 software. Pixel-cluster with P<0.001 for hypo- or hypermetabolism were displayed in parametric images. Covariance analysis with neuropsychiatric tests was calculated for each cluster. RESULTS: In week 12 of IFN-alpha treatment, significant hypometabolism with a decrease of local activity ranging from 8 to 12% was found in all patients bilaterally in the prefrontal cortex (BA 9), which correlated in a covariate analysis with changes in depression score as measured by Beck's Depression Inventory. Additionally, hypermetabolism with a maximum increase in local activity of 6-8% was seen in all patients in putamina as well as the left occipital region (BA 18). Before IFN-alpha treatment, only 1/11 patient showed depressive symptomatology. After 3 months of treatment, 6/11 patients were classified as having mild to moderate depressive symptoms (P<0.1; Wilcoxon test). CONCLUSIONS: Low-dose IFN-alpha therapy is associated with significant prefrontal hypometabolism. This hypometabolism covaried with depression score, but was even found in clinically non-depressed patients. These findings may reflect a possible predisposing factor for IFN-alpha associated neuropsychiatric syndromes and might contribute to a pathophysiological model of affective disorders, as endogenous IFN-alpha levels are elevated in a subset of psychotic patients during acute disease.

Adult↗
PubMed2000

Coordination between breathing and forearm movements during sinusoidal tracking.

Time relationships (coordination) between breathing and rhythmical limb movements were analyzed during sinusoidal tracking movements of the forearm in 11 healthy subjects. The tracking rate was varied systematically between 0.1 and 1.0 Hz in 0.1-Hz steps. The aim of the study was to elucidate whether rhythmical tracking movements can entrain breathing, and whether this entrainment depends upon the movement rate. Subjects exhibited coordination between tracking movements and breathing at various rate ratios (1:1, 1:2, 1:3). At tracking rates of between 0.2 and 0.6 Hz, 1:1 coordination occurred with a maximum at 0.3 Hz; this rate range was called the 1:1 entrainment band. Coordination of 1:2 occurred at between 0.5 and 1. 0 Hz (the 1:2 coordination band) with a maximum at 0.7 Hz. Coordination of 1:3 could be detected at between 0.5 and 1.0 Hz. Different subjects showed 1:n entrainment bands at similar locations but different widths of the rate range studied. The breathing rate during tracking was significantly higher than at rest, and it was correlated positively with tracking rate. This correlation, however, depended upon the width of the entrainment bands. Breathing rates varied between 0.2 and 0.6 Hz for all coordination patterns. We conclude that the occurrence of fixed time relationships is an expression of the strength of central nervous system coupling between the two processes. The frequency of coordination between breathing and rhythmical tracking movements depends critically upon the movement rate.

Adult↗
PubMed2000

Sex, linkage disequilibrium and patterns of parasitism in three species of cyclically parthenogenetic Daphnia (Cladocera: Crustacea).

To gain insight into genetic variation for resistance to parasites, this study assayed clonal variation in cyclically parthenogenetic Daphnia magna with respect to parasitic infection. Samples were collected from natural populations, and the allozyme phenotypes of infected hosts were compared to those of uninfected hosts. Differences between the clonal composition of the infected and uninfected class were evident in only two of 16 populations examined. This result stands in contrast to a study of species in the D. pulex and D. longispina species complexes, where clonal variation for infection was found in 12 of 25 populations (Little & Ebert, 1999). Considering all populations from both studies, associations between host genotype and infection were typically evident only in populations that showed low genotypic diversity and evidence of genetic disequilibria, with D. magna showing the least amount of disequilibria. This pattern is compatible with at least two possibly overlapping hypotheses. First, it may be that those populations lacking clonal variation for infection experienced weaker parasite-mediated selection. We can not rule out variation in selection pressure as an explanation, but found no evidence that the prevalence or intensity of parasitism differed either among species, or between those populations which showed clonal variation for infection and those that did not. Second, it could be that some populations, especially those of D. magna, have more frequent sexual recruitment than others. Sexual recombination breaks up gene combinations which are in linkage disequilibrium, and our method to detect clonal variation for resistance relies on linkage between genetic markers (allozymes) and resistance loci. Past work on Daphnia has shown that the level of sexual recruitment (which is in turn mediated by habitat permanency) is indeed commonly linked to the occurrence of genetic disequilibria. Our results may thus underestimate the prevalence of clonal variation for infection (especially for D. magna), because most of the populations analysed appeared to have high levels of sexual recruitment and therefore lacked the linkage disequilibrium that underlies associations between allozymes and susceptibility.

Animals↗
PubMed1999

Stents for the treatment of aortic aneurysms. Review of devices, technique and results.

The endovascular treatment of abdominal aortic aneurysms has generated a great deal of interest since the early 1990s, and many different devices are currently available. The procedure of endovascular repair has been evaluated in many institutions and the different devices are compared. The first results were encouraging, but complications like endoleak, dislocation or thrombosis of the graft occurred. By the available devices the stent application is only promising, if the known exclusion criteria are strictly respected. Therefore a careful preinterventional assessment of the patient by different imaging modalities is necessary. As the available results up to now are preliminary and the durability of the devices has to be controlled, multicenter studies are required to improve the devices and observe their long-term success in the exclusion of abdominal aortic aneurysms.

Aortic Aneurysm↗