Characterization of Giardia cell nucleus：Its implication on the nature and origin of the primitive cell nucleus

Thecentralproblemoftheoriginandearlyevolutionoftheeukaryoticcel1istheoriginofthecellnucleus,becausethecellnucleus,withitsdouble-layerednuclearenvelope,isthemostprominentandimportantmorphologicalmarkdistinguishingeukaryoticcellsfromprokaryotes.Eukaryoticcellsmayhavenochloroplast,mito-chondriaorflagellum,buttheymustpossessacellnucleus.Thecellnucleusitselfisaverycomplicatedstructure-Ifwetrytomakecleartheoriginandearlyevolutionofthecellnucleus,weoughttoinvestigatetheoriginandevolutionofeachmorphol…     

Functional and metabolic assessment of the blood cell’s response to exposure to local vibration

Physiological characteristics of blood cells in workers exposed to long-term local vibration were studied. The total cell peroxidase activity, the level of the phagocytic response, neutrophil alkaline phosphatase and acid phosphatase activity levels, and glycogen content in neutrophils and lymphocytes were measured. Changes associated with a decrease in the functional metabolic parameters, depending on the duration of contact with vibrating tools and the severity of clinical symptoms, were detected. The detected differences in changes in cell response may reflect the specific features of the mechanisms of adaptive regulation.     

Composite mathematical modeling of calcium signaling behind neuronal cell death in Alzheimer’s disease

Background

Alzheimer’s disease (AD) is a progressive neurological disorder, recognized as the most common cause of dementia affecting people aged 65 and above. AD is characterized by an increase in amyloid metabolism, and by the misfolding and deposition of β-amyloid oligomers in and around neurons in the brain. These processes remodel the calcium signaling mechanism in neurons, leading to cell death via apoptosis. Despite accumulating knowledge about the biological processes underlying AD, mathematical models to date are restricted to depicting only a small portion of the pathology.

Results

Here, we integrated multiple mathematical models to analyze and understand the relationship among amyloid depositions, calcium signaling and mitochondrial permeability transition pore (PTP) related cell apoptosis in AD. The model was used to simulate calcium dynamics in the absence and presence of AD. In the absence of AD, i.e. without β-amyloid deposition, mitochondrial and cytosolic calcium level remains in the low resting concentration. However, our in silico simulation of the presence of AD with the β-amyloid deposition, shows an increase in the entry of calcium ions into the cell and dysregulation of Ca ²⁺ channel receptors on the Endoplasmic Reticulum. This composite model enabled us to make simulation that is not possible to measure experimentally.

Conclusions

Our mathematical model depicting the mechanisms affecting calcium signaling in neurons can help understand AD at the systems level and has potential for diagnostic and therapeutic applications.

     

Maps of interaural time difference in the chicken’s brainstem nucleus laminaris

Animals, including humans, use interaural time differences (ITDs) that arise from different sound path lengths to the two ears as a cue of horizontal sound source location. The nature of the neural code for ITD is still controversial. Current models differentiate between two population codes: either a map-like rate-place code of ITD along an array of neurons, consistent with a large body of data in the barn owl, or a population rate code, consistent with data from small mammals. Recently, it was proposed that these different codes reflect optimal coding strategies that depend on head size and sound frequency. The chicken makes an excellent test case of this proposal because its physical prerequisites are similar to small mammals, yet it shares a more recent common ancestry with the owl. We show here that, like in the barn owl, the brainstem nucleus laminaris in mature chickens displayed the major features of a place code of ITD. ITD was topographically represented in the maximal responses of neurons along each isofrequency band, covering approximately the contralateral acoustic hemisphere. Furthermore, the represented ITD range appeared to change with frequency, consistent with a pressure gradient receiver mechanism in the avian middle ear. At very low frequencies, below 400 Hz, maximal neural responses were symmetrically distributed around zero ITD and it remained unclear whether there was a topographic representation. These findings do not agree with the above predictions for optimal coding and thus revive the discussion as to what determines the neural coding strategies for ITDs.     

The nervous system of Bothriomolus balticus (Proseriata) —a contribution to the knowledge of the orthogon in the Plathelminthes

Summary The nervous system (NS) of Bothriomolus balticus (Proseriata) was studied by the immunocytochemical (ICC) method with antisera to RFamide, SALMFamide and serotonin and with the histochemical GAIF method. The use of the ICC technique provided a much more precise morphological account of the nervous system than had previously been possible. The obtained data are discussed in connection with the comparative morphology of the nerve cords of the Plathelminthes. A similar position does not grant direct correspondence between nerve cords in the taxon Seriata. Marginal cords had probably an independent origin in the Monocelididae and Otoplanidae. The ventral (main) cords of B. balticus seem to correspond to the lateral (main) cords of the Monocelididae. It can be hypothesized that both: (1) a shift of the main cords accompanied by formation of new cords from the plexus and fusion of other cords and (2) a redistribution of nerve processes and perikarya between the cords, take part in the evolution of cords in the Plathelminthes. The first hypothesis seems to explain the difference in the position of main cords in proseriates, though, the second hypothesis might dominate, for example, in the Neorhabdocoela and the Neodermata. The correctness of the evolutionary analysis of the nerve cords in plathelminths can only be provided by neurons or neuron groups marking these structures.     

Study of neuronal organization of the “gastric” region in the dorsal motor nucleus of the vagus nerve

The peculiarities of neuronal electrical activity in the dorsal motor nucleus (0.5–2.0 mm rostrally to the obex) were investigated in acute experiments on cats, using the microelectrode technique, under conditions of stimulation of the gastric vagal branches. In the gastric region of the nucleus, two groups of cells responding to nerve stimulation were identified: preganglionic parasympathetic neurons antidromically activated by such stimulation, and cells excited orthodromically with the involvement of afferent fibers of the vagus nerve.Neirofiziologiya/Neurophysiology, Vol. 25, No. 3, pp. 190–196, May-June, 1993.     

E.V. Ananiev’s contribution to studies of the centromere and construction of an artificial plant chromosome

The plant centromere has been described to consist of blocks of repetitive DNA sequences, and self-assembly of an artificial plant chromosome has been achieved using individual cloned elements. E.V. Ananiev’s contribution to these studies is described.     

Zooplankton communities of the Arctic’s Canada Basin: the contribution by smaller taxa

Zooplankton was sampled at ten stations in the Canada Basin during August 2002 using both 53- and 236-m mesh nets to examine the contribution by smaller and less studied species. Copepod nauplii, the copepods Oithona similis, Oncaea borealis and Microcalanus pygmaeus, and the larvacean Fritillaria borealis typica dominated the upper 100 m of the water column numerically, while biomass was dominated by the copepods Calanus hyperboreus, Calanus glacialis and Paraeuchaeta glacialis, and the chaetognath Eukrohnia hamata. Zooplankton biomass ranged from 3.7 to 14.5 mg AFDW m^–3, with a mean of 9.6 mg AFDW m^–3 . While the three microcopepods contributed less than 5% of the biomass, estimates of their potential growth rates suggest they might contribute upwards of 25% of the metazoan zooplankton production. The true rates of growth and development of these microcopepods in the Arctic need to be determined to conclusively ascertain their importance.     

Endosymbiosis of Chlorella species to the ciliate Paramecium bursaria alters the distribution of the host’s trichocysts beneath the host cell cortex

Each symbiotic Chlorella of the ciliate Paramecium bursaria is enclosed in a perialgal vacuole membrane derived from the host digestive vacuole membrane. Alga-free paramecia and symbiotic algae can grow independently. Mixing them experimentally can cause reinfection. Earlier, we reported that the symbiotic algae appear to push the host trichocysts aside to become fixed beneath the host cell cortex during the algal reinfection process. Indirect immunofluorescence microscopy with a monoclonal antibody against the trichocysts demonstrates that the trichocysts change their locality to form algal attachment sites and decrease their density beneath the host cell cortex through algal reinfection. Transmission electron microscopy to detect acid phosphatase activity showed that some trichocysts near the host cell cortex are digested by the host lysosomal fusion during algal reinfection. Removal of algae from the host cell using cycloheximide recovers the trichocyst's arrangement and number near the host cell cortex. These results indicate that symbiotic algae compete for their attachment sites with preexisting trichocysts and that the algae have the ability to ensure algal attachment sites beneath the host cell cortex.     

Crohn’s disease of the colon: ultrastructural changes in submuscular interstitial cells of Cajal

Interstitial cells of Cajal (ICC) at the submuscular border of the human colon (ICC-SMP) are the proposed pacemaker cells of the musculature. In patients with Crohn’s disease (CD) of the colon, ICC-SMP showed characteristic cytological changes from controls. The changes comprised secondary lysosomes in connection with lipid droplets and cytoplasmic vacuoles or multiple empty, confluent and often outbulging vacuoles merging with cisterns of granular endoplasmic reticulum and clusters of glycogen granules. These changes were most pronounced in patients with macroscopical mucosal inflammation but were also demonstrable in uninvolved colonic segments. Relationships of ICC to other cells were undisturbed. The changes were selective to ICC-SMP, as glial cells, muscle cells and fibroblast-like cells at the submuscular border showed no cytological alterations compared with controls. Varicosities of the submuscular plexus were often empty and dilated. Fibroblast-like cells selectively encased macrophages and mast cells. The cytological changes in ICC-SMP in CD are thus similar to changes seen in ulcerative colitis and may be of pathophysiological significance with regard to the motility and sensory disturbances seen in patients with CD.     

The regulatory role of α-synuclein and parkin in neuronal cell apoptosis; possible implications for the pathogenesis of Parkinson’s disease

Parkinson’s disease (PD) is the second most common progressive neurodegenerative disorder beyond Alzheimer’s disease, affecting approximately 1% of people over the age of 65. The major pathological hallmarks of PD are significant loss of nigrostriatal dopaminergic (DA) neurons and the presence of intraneuronal protein inclusions termed Lewy bodies. Sporadic cases represent more than 90% of total patients with PD, while there exist several inherited forms caused by mutations in single genes. Identification and characterization of these causative genes and their products can help us understand the molecular mechanisms of DA neuronal cell death and design new approaches to treat both the inherited and sporadic forms of PD. Based on the finding that a point mutation in the gene encoding α-synuclein (αSyn) protein causes a rare familial form of PD, PARK1, it is now confirmed that αSyn is a major component of Lewy bodies in patients with sporadic PD. Abnormal accumulation of αSyn protein is considered a neurotoxic event in the development of PD. PARK4, another dominantly inherited form of familial PD, is caused by duplication or triplication of the αSyn gene locus. This genetic mutation results in the production of large amounts of wild-type αSyn protein, supporting the αSyn-induced neurodegeneration hypothesis. On the other hand, the recessively inherited early-onset Parkinsonism is caused in about half of the cases with loss-of-function mutations in PARK2, which encodes E3 ubiquitin ligase parkin in the ubiquitin–proteasome system. These findings have shed light on DA neurodegeneration caused by accumulation of toxic protein species that can be degraded and/or detoxicated through parkin activity. In this review, we will focus on the regulatory roles of αSyn and parkin proteins in DA neuronal cell apoptosis and provide evidence for the possible therapeutic action of parkin in sporadic patients with PD.     

Power,knowledge and Black Feminist Thought’s enduring contribution towards social justice

In this review, I focus on three themes approached in Patricia Hill Collins’s Black Feminist Thought – difference and inequality, knowledge and power, and black feminist thought and black women intellectuals – in order to argue that what makes it a unique work is the fact that it features an original framework that grapples with epistemological and conceptual issues in order to grasp black women’s intellectual legacy.     

Fast rearrangement of the neuronal growth cone’s actin cytoskeleton following VEGF stimulation

The neuronal growth cone plays a crucial role in the development of the nervous system. This highly motile structure leads the axon to its final destination by translating guidance cues into cytoskeletal rearrangements. Recently, vascular endothelial growth factor (VEGF), which is essential for angiogenesis and vascular sprouting, has been found to exert a trophic activity also on neurons, leading to an increased axonal outgrowth, similar to the well-known nerve growth factor (NGF). The neurotrophic properties of VEGF are likely to be promoted via the VEGF receptor 2 (VEGFR-2) and neuropilin-1 (NRP-1). In the long term, VEGF attracts and influences the growth cone velocity and leads to growth cone enlargement. The present study focuses on immediate VEGF effects using RFP-actin and GFP-NF-M microinjected chicken dorsal root ganglia for live cell imaging of the neuronal growth cone. We analyzed actin and neurofilament dynamics following VEGF and NGF treatment and compared the effects. Furthermore, key signaling pathways of VEGF were investigated by specific blocking of VEGFR-2 or NRP-1. With the aid of confocal laser scanning microscopy and stimulated emission depletion microscopy, we show for the first time that VEGF has a quick effect on the actin-cytoskeleton, since actin rearrangements were identifiable within a few minutes, leading to a dramatically increased motion. Moreover, these effects were strongly enhanced by adding both VEGF and NGF. Most notably, the effects were inhibited by blocking VEGFR-2, therefore we propose that the immediate effects of VEGF on the actin-cytoskeleton are mediated through VEGFR-2.     

Current approaches to the treatment of Parkinson’s Disease

Parkinson’s Disease (PD) is the second most common neurodegenerative disorder. Clinical approaches to manage PD include symptomatic therapies, serving to compensate for the effects of dopaminergic neuronal deficits, as well as more recently a move toward disease modification, with the goal of slowing or stopping disease progression. This perspective surveys the approved therapies for PD treatment as well as provides a view of the ongoing clinical approaches aimed at improving outcomes for PD patients.     

A histochemical approach to the knowledge about the neuron nucleus: The “pre-alarm chromatin”

Chromatin as a functional whole.Since the nineteen-fifties (1,2), studies on the histochemistry of the nucleus have been based on its concept as a whole: measurement of the DNA content, and the ratio between nucleus size and cell size appeared to be (and were in effect) an indication of the functional status of the single cell and of the cell population. Two decades later, the already well-known morphological distinction between the chromatins as euchromatin and heterochromatin was reinterpreted on the basis of the degree of spiralization of the nucleosomal fiber and its complexity (3). Subsequently, considerable information about the non-random interphasic position of the chromosomal domains in the nucleus was obtained by in situ hybridization, and the successive reconstruction of their location in the nucleus by image processing with Normarski optics and rotating stage or by confocal microscopy (4–8).Moreover, immunological studies using monoclonal antibodies raised against the splicing factors acting on nuclear pre-mRNAs in discrete nuclear regions (spliceosomes) (9,10), lent support to the notion that the chromatin machinery operates as a whole.Invited contribution to the Joint Meeting of the Universities of Milan, Pavia and Ulm, located in the European Regions of Lombardy (Italy) and Baden-Wurttemberg (Germany), on Cellular and Molecular Aspects of Neuronal Development, Ulm, April 5–8, 1992.