1,093 research outputs found
A REVISION OF THE AFRICAN GENERA PAROPSIOPSIS AND SMEATHMANNIA (PASSIFLORACEAE - PAROPSIEAE), INCLUDING A NEW SPECIES OF PAROPSIOPSIS FROM CAMEROON
The African genera Paropsiopsis Engl. and Smeathmannia R.Br. (Passifloraceae - Paropsieae) are revised. The two genera are well separated based on the presence or absence of a second, annuliform, corona, as well as the number of stamens and curvature of their filaments. An overview of important characters and a key to all genera of Paropsieae is provided. In Paropsiopsis all previously recognised species are united under P. decandra (Baill.) Sleumer. In addition one species, Paropsiopsis atrichogyna J.M.de Vos & Breteler, is newly described and illustrated. In Smeathmannia both previously recognised species are maintained, but infraspecific taxa are rejected. Descriptions of both genera and their species, keys to species, illustrations and distribution maps are provide
Phaeocystis blooming enhanced by copepod predation on protozoa: evidence from incubation experiments
Laboratory experiments were carried out to investigate the effect of protozoan, copepod and combined grazing on Phaeocystis biomass. Phaeocystis cf. globosa single cells were offered to 3 different protozoan species, to the calanoid copepod Temora longicornis, as well as to mixtures of both grazer types. The heterotrophic dinoflagellate Oxyrrhis marina and the oligotrich ciliate Strombidinopsis acuminatum ingested Phaeocystis at much higher rates than did the copepod. Nevertheless, protozoan growth and ingestion rates were submaximal, indicating Phaeocystis to be suboptimal food.
The oligotrich ciliate Strombidium elegans did not feed on Phaeocystis. In grazing experiments with mixtures of both predator types, the decline of Phaeocystis single cells could be explained by protozoan grazing alone, implying no grazing by the copepods on Phaeocystis. Instead, copepods ingested the protozoans at high rates. Predation on 0. marina and S. acuminatum by T. longicornis resulted in a
reduction of the total grazing pressure on Phaeocystis of 21 and 67 % respectively. We conclude that mesozooplankton predation on herbivorous ciliates and heterotrophic dinoflagellates, which consumed Phaeocystis cells, can considerably reduce the overall grazing pressure and may enhance Phaeocystis
bloomng
Incidence, risk, and case fatality of first ever stroke in the elderly population. The Rotterdam Study
OBJECTIVE: To estimate the incidence, survival, and lifetime risk of
stroke in the elderly population. METHODS: The authors conducted a study
in 7,721 participants from the population based Rotterdam Study who were
free from stroke at baseline (1990-1993) and were followed up for stroke
until 1 January 1999. Age and sex specific incidence, case fatality rates,
and lifetime risks of stroke were calculated. RESULTS: Mean follow up was
6.0 years and 432 strokes occurred. The incidence rate of stroke per 1,000
person years increased with age and ranged from 1.7 (95% CI 0.4 to 6.6) in
men aged 55 to 59 years to 69.8 (95% CI 22.5 to 216.6) in men aged 95
years or over. Corresponding figures for women were 1.2 (95% CI 0.3 to
4.7) and 33.1 (95% CI 17.8 to 61.6). Men and women had similar absolute
lifetime risks of stroke (21% for those aged 55 years). The survival after
stroke did not differ according to sex. CONCLUSIONS: Stroke incidence
increases with age, also in the very old. Although the incidence rate is
higher in men than in women over the entire age range, the lifetime risks
were similar for both sexes
Automated Olfactory Bulb Segmentation on High Resolutional T2-Weighted MRI
The neuroimage analysis community has neglected the automated segmentation of
the olfactory bulb (OB) despite its crucial role in olfactory function. The
lack of an automatic processing method for the OB can be explained by its
challenging properties. Nonetheless, recent advances in MRI acquisition
techniques and resolution have allowed raters to generate more reliable manual
annotations. Furthermore, the high accuracy of deep learning methods for
solving semantic segmentation problems provides us with an option to reliably
assess even small structures. In this work, we introduce a novel, fast, and
fully automated deep learning pipeline to accurately segment OB tissue on
sub-millimeter T2-weighted (T2w) whole-brain MR images. To this end, we
designed a three-stage pipeline: (1) Localization of a region containing both
OBs using FastSurferCNN, (2) Segmentation of OB tissue within the localized
region through four independent AttFastSurferCNN - a novel deep learning
architecture with a self-attention mechanism to improve modeling of contextual
information, and (3) Ensemble of the predicted label maps. The OB pipeline
exhibits high performance in terms of boundary delineation, OB localization,
and volume estimation across a wide range of ages in 203 participants of the
Rhineland Study. Moreover, it also generalizes to scans of an independent
dataset never encountered during training, the Human Connectome Project (HCP),
with different acquisition parameters and demographics, evaluated in 30 cases
at the native 0.7mm HCP resolution, and the default 0.8mm pipeline resolution.
We extensively validated our pipeline not only with respect to segmentation
accuracy but also to known OB volume effects, where it can sensitively
replicate age effects
FastSurfer-HypVINN: Automated sub-segmentation of the hypothalamus and adjacent structures on high-resolutional brain MRI
The hypothalamus plays a crucial role in the regulation of a broad range of
physiological, behavioural, and cognitive functions. However, despite its
importance, only a few small-scale neuroimaging studies have investigated its
substructures, likely due to the lack of fully automated segmentation tools to
address scalability and reproducibility issues of manual segmentation. While
the only previous attempt to automatically sub-segment the hypothalamus with a
neural network showed promise for 1.0 mm isotropic T1-weighted (T1w) MRI, there
is a need for an automated tool to sub-segment also high-resolutional (HiRes)
MR scans, as they are becoming widely available, and include structural detail
also from multi-modal MRI. We, therefore, introduce a novel, fast, and fully
automated deep learning method named HypVINN for sub-segmentation of the
hypothalamus and adjacent structures on 0.8 mm isotropic T1w and T2w brain MR
images that is robust to missing modalities. We extensively validate our model
with respect to segmentation accuracy, generalizability, in-session test-retest
reliability, and sensitivity to replicate hypothalamic volume effects (e.g.
sex-differences). The proposed method exhibits high segmentation performance
both for standalone T1w images as well as for T1w/T2w image pairs. Even with
the additional capability to accept flexible inputs, our model matches or
exceeds the performance of state-of-the-art methods with fixed inputs. We,
further, demonstrate the generalizability of our method in experiments with 1.0
mm MR scans from both the Rhineland Study and the UK Biobank. Finally, HypVINN
can perform the segmentation in less than a minute (GPU) and will be available
in the open source FastSurfer neuroimaging software suite, offering a
validated, efficient, and scalable solution for evaluating imaging-derived
phenotypes of the hypothalamus.Comment: Submitted to Imaging Neuroscienc
Homocysteine and brain atrophy on MRI of non-demented elderly
Patients with Alzheimer's disease have higher plasma homocysteine levels
than controls, but it is uncertain whether higher plasma homocysteine
levels are involved in the early pathogenesis of the disease. Hippocampal,
amygdalar and global brain atrophy on brain MRI have been proposed as
early markers of Alzheimer's disease. In the Rotterdam Scan Study, a
population-based study of age-related brain changes in 1077 non-demented
people aged 60-90 years, we investigated the association between plasma
homocysteine levels and severity of hippocampal, amygdalar and global
brain atrophy on MRI. We used axial T(1)-weighted MRIs to visualize global
cortical brain atrophy (measured semi-quantitatively; range 0-15) and a 3D
HASTE (half-Fourier acquisition single-shot turbo spin echo) sequence in
511 participants to measure hippocampal and amygdalar volumes. We had
non-fasting plasma homocysteine levels in 1031 of the participants and in
505 of the participants with hippocampal and amygdalar volumes.
Individuals with higher plasma homocysteine levels had, on average, more
cortical atrophy [0.23 units (95% CI 0.07-0.38 units) per standard
deviation increase in plasma homocysteine levels] and more hippocampal
atrophy [difference in left hippocampal volume -0.05 ml (95% CI -0.09 to
-0.01) and in right hippocampal volume -0.03 ml (95% CI -0.07 to 0.01) per
standard deviation increase in plasma homocysteine levels]. No association
was observed between plasma homocysteine levels and amygdalar atrophy.
These results support the hypothesis that higher plasma homocysteine
levels are associated with more atrophy of the hippocampus and cortical
regions in elderly at risk of Alzheimer's disease
Psychomotor Retardation and the prognosis of antidepressant treatment in patients with unipolar Psychotic Depression
Background: Psychomotor Retardation is a key symptom of Major Depressive Disorder. According to the literature its presence may affect the prognosis of treatment. Aim of the present study is to investigate the prognostic role of Psychomotor Retardation in patients with unipolar Psychotic Depression who are under antidepressant treatment. Methods: The Salpetriere Retardation Rating Scale was administered at baseline and after 6 weeks to 122 patients with unipolar Psychotic Depression who were randomly allocated to treatment with imipramine, venlafaxine or venlafaxine plus quetiapine. We studied the effects of Psychomotor Retardation on both depression and psychosis related outcome measures. Results: 73% of the patients had Psychomotor Retardation at baseline against 35% after six weeks of treatment. The presence of Psychomotor Retardation predicted lower depression remission rates in addition to a higher persistence of delusions. After six weeks of treatment, venlafaxine was associated with higher levels of Psychomotor Retardation compared to imipramine and venlafaxine plus quetiapine. Conclusions: Our data confirm that Psychomotor Retardation is a severity marker of unipolar Psychotic Depression. It is highly prevalent and predicts lower effectivity of antidepressant psychopharmacological treatment
Cognitive dysfunction in naturally occurring canine idiopathic epilepsy
Globally, epilepsy is a common serious brain disorder. In addition to seizure activity, epilepsy is associated with cognitive impairments including static cognitive impairments present at onset, progressive seizure-induced impairments and co-morbid dementia. Epilepsy occurs naturally in domestic dogs but its impact on canine cognition has yet to be studied, despite canine cognitive dysfunction (CCD) recognised as a spontaneous model of dementia. Here we use data from a psychometrically validated tool, the canine cognitive dysfunction rating (CCDR) scale, to compare cognitive dysfunction in dogs diagnosed with idiopathic epilepsy (IE) with controls while accounting for age. An online cross-sectional study resulted in a sample of 4051 dogs, of which n = 286 had been diagnosed with IE. Four factors were significantly associated with a diagnosis of CCD (above the diagnostic cut-off of CCDR ≥50): (i) epilepsy diagnosis: dogs with epilepsy were at higher risk; (ii) age: older dogs were at higher risk; (iii) weight: lighter dogs (kg) were at higher risk; (iv) training history: dogs with more exposure to training activities were at lower risk. Impairments in memory were most common in dogs with IE, but progression of impairments was not observed compared to controls. A significant interaction between epilepsy and age was identified, with IE dogs exhibiting a higher risk of CCD at a young age, while control dogs followed the expected pattern of low-risk throughout middle age, with risk increasing exponentially in geriatric years. Within the IE sub-population, dogs with a history of cluster seizures and high seizure frequency had higher CCDR scores. The age of onset, nature and progression of cognitive impairment in the current IE dogs appear divergent from those classically seen in CCD. Longitudinal monitoring of cognitive function from seizure onset is required to further characterise these impairments
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