Optimising adjacent membrane segmentation and parameterisation in multicellular aggregates by piecewise active contours.

In fluorescence microscopy imaging, the segmentation of adjacent cell membranes within cell aggregates, multicellular samples, tissue, organs, or whole organisms remains a challenging task. The lipid bilayer is a very thin membrane when compared to the wavelength of photons in the visual spectra. Fluorescent molecules or proteins used for labelling membranes provide a limited signal intensity, and light scattering in combination with sample dynamics during in vivo imaging lead to poor or ambivalent signal patterns that hinder precise localisation of the membrane sheets. In the proximity of cells, membranes approach and distance each other. Here, the presence of membrane protrusions such as blebs; filopodia and lamellipodia; microvilli; or membrane vesicle trafficking, lead to a plurality of signal patterns, and the accurate localisation of two adjacent membranes becomes difficult. Several computational methods for membrane segmentation have been introduced. However, few of them specifically consider the accurate detection of adjacent membranes. In this article we present ALPACA (ALgorithm for Piecewise Adjacent Contour Adjustment), a novel method based on 2D piecewise parametric active contours that allows: (i) a definition of proximity for adjacent contours, (ii) a precise detection of adjacent, nonadjacent, and overlapping contour sections, (iii) the definition of a polyline for an optimised shared contour within adjacent sections and (iv) a solution for connecting adjacent and nonadjacent sections under the constraint of preserving the inherent cell morphology. We show that ALPACA leads to a precise quantification of adjacent and nonadjacent membrane zones in regular hexagons and live image sequences of cells of the parapineal organ during zebrafish embryo development. The algorithm detects and corrects adjacent, nonadjacent, and overlapping contour sections within a selected adjacency distance d, calculates shared contour sections for neighbouring cells with minimum alterations of the contour characteristics, and presents piecewise active contour solutions, preserving the contour shape and the overall cell morphology. ALPACA quantifies adjacent contours and can improve the meshing of 3D surfaces, the determination of forces, or tracking of contours in combination with previously published algorithms. We discuss pitfalls, strengths, and limits of our approach, and present a guideline to take the best decision for varying experimental conditions for in vivo microscopy.

Computational methods for analysis of dynamic events in cell migration.

Cell migration is a complex biological process that involves changes in shape and organization at the sub-cellular, cellular, and supra-cellular levels. Individual and collective cell migration can be assessed in vitro and in vivo starting from the flagellar driven movement of single sperm cells or bacteria, bacterial gliding and swarming, and amoeboid movement to the orchestrated movement of collective cell migration. One key technology to access migration phenomena is the combination of optical microscopy with image processing algorithms. This approach resolves simple motion estimation (e.g. preferred direction of migrating cells or path characteristics), but can also reveal more complex descriptors (e.g. protrusions or cellular deformations). In order to ensure an accurate quantification, the phenomena under study, their complexity, and the required level of description need to be addressed by an adequate experimental setup and processing pipeline. Here, we review typical workflows for processing starting with image acquisition, restoration (noise and artifact removal, signal enhancement), registration, analysis (object detection, segmentation and characterization) and interpretation (high level understanding). Image processing approaches for quantitative description of cell migration in 2- and 3-dimensional image series, including registration, segmentation, shape and topology description, tracking and motion fields are presented. We discuss advantages, limitations and suitability for different approaches and levels of description.

Cholinergic markers in the cortex and hippocampus of some animal species and their correlation to Alzheimer's disease.

INTRODUCTION: The cholinergic system includes neurons located in the basal forebrain and their long axons that reach the cerebral cortex and the hippocampus. This system modulates cognitive function. In Alzheimer's disease (AD) and ageing, cognitive impairment is associated with progressive damage to cholinergic fibres, which leads us to the cholinergic hypothesis for AD. DEVELOPMENT: The AD produces alterations in the expression and activity of acetyltransferase (ChAT) and acetyl cholinesterase (AChE), enzymes specifically related to cholinergic system function. Both proteins play a role in cholinergic transmission, which is altered in both the cerebral cortex and the hippocampus due to ageing and AD. Dementia disorders are associated with the severe destruction and disorganisation of the cholinergic projections extending to both structures. Specific markers, such as anti-ChAT and anti-AChE antibodies, have been used in light immunohistochemistry and electron microscopy assays to study this system in adult members of certain animal species. CONCLUSIONS: This paper reviews the main immunomorphological studies of the cerebral cortex and hippocampus in some animal species with particular emphasis on the cholinergic system and its relationship with the AD.

Effects of mid-summer transport duration on pre- and post-slaughter performance and pork quality in Mexico.

Seven hundred and fourteen pigs were monitored from transport to slaughter in July in three treatments: 8, 16 and 24 transport hours; lairage time for the three groups was of 8h. Transport duration significantly (P<0.05) affected live-weight gain during the rest period. Weight gain percentages at lairage were 0.05%, 0.78% and 1.15% for treatments 1, 2 and 3, respectively. Transport to slaughter loss percentage was 2.7%, 4.3% and 6.8% for each of the treatments. Short transport periods significantly increased carcass pH below normal values. Animals transported under acute stress (8h) showed pale carcasses (high possibilities of transforming into PSE meat). On the contrary, pigs transported for 24h had more dark red carcasses. Transport from farm to the slaughterhouse should take no more than 16h in order to improve carcass quality and animals' welfare.

Growth hormone response to growth hormone-releasing hormone in schizophrenic patients.

Ten schizophrenic patients and five normal control subjects were challenged with growth hormone-releasing hormone in a pilot study investigating growth hormone secretion from the pituitary. The results suggest suprapituitary dysfunction in schizophrenia, but replication in a larger study is needed.

Gonadal hormones, sex and behavior.

Gender differences have been demonstrated in several regions of the central nervous system (CNS) in animals and humans. These differences change with development and aging and are probably influenced by hormones. Gender differences have been demonstrated clinically in the prevalence of some mental disorders and responses to psychotropic medications. Gonadal hormones might be involved in these differences as well as in differential cognitive functions. The two genders also differ in the aging process. While it is well known that changes in the pituitary gonadal system influence the aging process in women, preliminary data described here demonstrate the association between pituitary-gonadal hormones and the aging process of sexual desire and activity in men. The changes in levels of gonadal hormones might contribute to the pathophysiology of dysphoric cyclic disorders and increased vulnerability to affective disorders in women. This vulnerability might be related to hormonal fluctuations over time as well as to alteration in internal oscillators and time-related functions.

Plasma dexamethasone and cortisol levels in depressed outpatients.

We investigated the 1-mg dexamethasone suppression test (DST) in 41 outpatients with major depressive disorder assessing the role of dexamethasone blood level, age and basal cortisol on DST results. Non-suppressors (approximately 25% of patients) had lower dexamethasone levels, and post-dexamethasone cortisol was negatively correlated with plasma dexamethasone; these findings were more significant after covarying out age and basal cortisol, factors that were also significantly associated to non-suppressors. A subgroup of patients (n = 19) also had 0.75-mg and 2.0-mg DST to evaluate whether a threshold dexamethasone blood level existed; a dexamethasone blood level greater than 1.5 ng/ml converted all non-suppressors to suppressors. Implications of these findings are discussed.

Clinical variables and hypothalamic-pituitary-adrenal function in depression. The importance of mood reactivity.

Forty outpatients with major depressive disorder were studied with the 1 mg DST and the Afternoon Cortisol Test. No relationship was found between hypothalamic-pituitary-adrenal (HPA) axis function and Research Diagnostic Criteria subtypes of depression, with the exception of higher log post-dexamethasone cortisol levels in endogenous depressives. Patients with mood reactivity had lower cortisol values on all assessments. The data suggest that the presence of mood reactivity may be useful as a predictor of normal HPA function in depression.

Therapeutic indications for serotonin-potentiating compounds: a hypothesis.

The original antidepressants, tricyclics and MAO inhibitors, increase the availability in the brain of both 5-HT and NA. Prompted by clinical findings suggestive of 5-HT disturbances in depression, drugs were developed that increase 5-HT selectively. Data are presented that suggest that broad-spectrum compounds may provide better conditions for antidepressant effects than the 5-HT-selective ones. The hypothesis is proposed that 5-HT potentiators are partial antidepressants, in that they predominantly reduce the anxiety/aggressive component of the depressive syndrome, and deserve to be tested in conditions with heightened anxiety and/or aggression irrespective of the nosological diagnosis. Tentative evidence relates diminished 5-HT metabolism to disordered impulse control. Based on these data, trials of 5-HT potentiators in impulse control disorders unrelated to aggressive drives seem warranted.

Hormonal probes of central serotonergic activity: do they really exist?

The response of a hormone allegedly under 5-hydroxytryptaminergic (5-HT-ergic) control to a compound stimulating or inhibiting serotonergic activity has been used as a measure of the functional state of central serotonergic systems. The relevant literature is reviewed, and based on that, it is concluded that, as yet, no reliable hormonal 5-HT probe exists. The main problems are nonselectivity of the challengers and noncomparability of individual studies because of variations in dose and route of administration. An acceptable hormonal 5-HT probe should at least have passed the following three tests. The influence of the challenger on catecholaminergic (CA) systems must be rendered unlikely in humans to avoid the pitfalls of, say, the 5-HT precursors whose CA-ergic influences have been overlooked. Dose-response relationships must be established to avoid the confusion caused by different investigators using the challenger in different doses. It must be demonstrated that the effect of the challenger is counteracted by its functional opponent.

Dexamethasone suppression test in schizophrenia. A study and review.

The prevalence of an abnormal response to the 1 mg dexamethasone suppression test (DST) was examined in 40 inpatients suffering from a major depressive disorder (MDD), 17 inpatients suffering from schizophrenia, and 30 normal controls. 23.5% of the schizophrenics were DST nonsuppressors compared to 52.5% of MDD patients and 6.7% of normal controls. The prevalence of abnormal DST in schizophrenics in the literature is reviewed and factors like the presence of depression, doses of dexamethasone, and hospital admission, which may account for the wide variability of prevalence among studies (0-35%), are discussed.