Structure and synaptic organization of the osphradium of the lamellibranch mollusk Unio pectorum

The osphradial organ has been studied in Lamellibranchia--Unio pectorum--by means of scanning and transmissive electron microscopy. On the surface of the distal part of this hemosensory organ there is a distinct division into zones. The central part of the osphradial torus is occupied by the receptory zone, formed predominantly by supporting cells with microvilli and by peripheral processes of the subepithelial receptory cells. The lateral surfaces are occupied with ciliar areas of the ciliar supporting cells. In the receptory zone two types of the peripheral processes of the receptory cells are identified; they differ by the number of kinocilia and by ultrastructural organization of the apical part. Axon-like processes of the receptory cells interact with axons and dendrites of the ganglionic cells, forming axo-axonal, axodendritic and axosomatic synapses. The facts revealed demonstrate a high level of specialization of the osphradial receptory surface, connected with polymodality of this organ.     

Poly(ADP-ribose) synthesis is involved in the toxic effects of alkylating agents but does not regulate DNA repair

Poly(ADP-ribose) is a nuclear polymer that is synthesized in response to DNA-strand breaks and covently modifies numerous nuclear proteins. Inhibition of poly(ADP-ribose) polymerase by 3-amino-benzamide in cells exposed to DNA-damaging agents has a variety of cellular effects, including increases in cell killing, frequency of single-strand breaks, reapir replication, and sister-chromatid exchange. These increases have been interpreted as an indication that poly(ADP-ribose) polymerization regulates the rate of ligation. Because of slow ligation, continued repair polymerization should therefore generate longer repair patches. Direct measurement of the rate of ligation of intracellular repair patches and of the size of repair patches indicates that they are unchanged when poly(ADP-ribose) polymerization is inhibited. We therefore conclude that poly(ADP-ribose) does not regulate the ligation stage of repair but instead may regulate the activity of intracellular nucleases and other enzymes that can cause additional DNA damage and changes in chromatin struture.     

Hsp70 Architecture: The Formation of Novel Polymeric Structures of Hsp70.1 and Hsc70 after Proteotoxic Stress

Heat induces Hsp70.1 (HSPA1) and Hsc70 (HSPA8) to form complex detergent insoluble cytoplasmic and nuclear structures that are distinct from the cytoskeleton and internal cell membranes. These novel structures have not been observed by earlier immunofluorescence studies as they are obscured by the abundance of soluble Hsp70.1/Hsc70 present in cells. While resistant to detergents, these Hsp70 structures display complex intracellular dynamics and are efficiently disaggregated by ATP, indicating that this pool of Hsp70.1/Hsc70 retains native function and regulation. Hsp70.1 promotes the repair of proteotoxic damage and cell survival after stress. In heated fibroblasts expressing Hsp70.1, Hsp70.1 and Hsc70 complexes are efficiently disaggregated before the cells undergo-heat induced apoptosis. In the absence of Hsp70.1, fibroblasts have increased rates of heat-induced apoptosis and maintain stable insoluble Hsc70 structures. The differences in the intracellular distribution of Hsp70.1 and Hsc70, combined with the ability of Hsp70.1, but not Hsc70, to promote the disaggregation of insoluble Hsp70.1/Hsc70 complexes, indicate that these two closely related proteins perform distinctly different cellular functions in heated cells.     

Features of the intracellular repair of irradiated keratinocytes

By means of light and electron microscopy, intracellular reparation has been studied after a local x-ray radiation of the rat paws (7.74 X 10(-1) Ci/kg) using radioprotectors (mexamin, cysteamin, ionol) and other chemical compounds (including membranoprotective ones). Restoration of the intracellular structures after x-ray burns proceeds more slowly and more complexly than reparation of the epidermis as a tissue system. To the slowly repairing intracellular formations belong mitochondria and, especially, internal mitochondrial membrane, as well as intercellular contacts. Under radiation mitochondria increase their volume at the expense of their three-fold swelling. Preliminary treatment of the skin with some of the compounds mentioned above decreases or completely prevents these changes. By means of the membranoactive chemical compounds, as well as by means of the known radioprotectors it is possible essentially to normalize the process of intracellular reparation and physiological regeneration of the ultrastructures, and in some cases, to stimulate reparative processes in them.     

Isolation of a cell-fusion hormone from Griffithsia pacifica kylin,a red alga

Filaments of Griffithsia pacifica replace dead cells by the process of cell repair. When an intercalary cell is killed, but its cell wall remains intact holding the two halves of the plant together, the cell above it produces a repair rhizoid cell; the cell below it produces a specialized, rhizoid-like repair shoot cell. The repair rhizoid and shoot grow towards each other, meet, and fuse to form a single shoot cell. Evidence from observations of cell repair in vivo has indicated that the repair rhizoid produces a hormone or hormones which induce the production of the repair shoot, maintain the rhizoid-like morphology and growth of the repair shoot, and attract it to the repair rhizoid for fusion. This hormone has been named rhodomorphin. Using an artificial cell-fusion system we show that repair rhizoids and normal rhizoids, but no shoot cell, can induce decapitated filaments to form repair shoot cells. Decapitated filaments form repair shoot cells only when they are exposed to the hormone within 4–6 h after decapitation; after this time they lose their sensitivity to the hormone. A method has been developed for isolating, and assaying for, the cell-fusion hormone. Rhodomorphin retains its activity for several days at room temperature and for at least two years at-16° C.     

热休克蛋白70在心血管疾病中的保护作用

热休克蛋白(heat shock protein70,HSP70)是HSP家族中重要成员,在生物细胞中含量最高,可诱导性最强,具有保护细胞免受刺激损伤,促进受损细胞修复及抗炎、抗凋亡、耐受缺血/缺氧损伤等多种生物学功能。许多研究发现在心肌组织中HSP70表达升高可减轻心肌细胞损伤程度,利于损伤心肌细胞的恢复,在预防和延缓心血管疾病中起到重要作用。因此,热休克蛋白70诱导剂在心血管疾病的防治中具有潜在的临床价值。本文主要对HSP70在心血管疾病中的保护作用进行综述。     

Biology and clinical applications of mesenchymal stem cells

Stem cell populations are found in most adult tissues and, in general, their differentiation potential may reflect the local cell population. Hematopoietic, epidermal, mesenchymal, neural and hepatic stem cells have been described. It may be that, in the adult, these cells are the reservoirs of reparative cells that are mobilized following injury and migrate to the wound site where, in cooperation with local cells, they participate in the repair response. Mesenchymal stem cells, isolated from the bone marrow, have the capacity to differentiate into cells of connective tissues. Some striking examples of the therapeutic use of MSCs have been reported recently in applications such as coronary artery disease, spinal cord injury, Parkinson's Disease, and liver regeneration. In orthopaedic medicine, MSC therapy has been applied in bone and cartilage repair and in the treatment of osteoarthritis. The question of the host response to implanted MSCs is critical as these cells are being evaluated in clinical applications. There are several aspects to the implanted cell-host interaction that need to be addressed as we attempt to understand the mechanisms underlying stem cell therapies. These are (1) the host immune response to implanted cells, (2) the homing mechanisms that guide delivered cells to a site of injury, and (3) differentiation of implanted cells under the influence of local signals.     

Inflammatory processes in muscle injury and repair

Modified muscle use or injury can produce a stereotypic inflammatory response in which neutrophils rapidly invade, followed by macrophages. This inflammatory response coincides with muscle repair, regeneration, and growth, which involve activation and proliferation of satellite cells, followed by their terminal differentiation. Recent investigations have begun to explore the relationship between inflammatory cell functions and skeletal muscle injury and repair by using genetically modified animal models, antibody depletions of specific inflammatory cell populations, or expression profiling of inflamed muscle after injury. These studies have contributed to a complex picture in which inflammatory cells promote both injury and repair, through the combined actions of free radicals, growth factors, and chemokines. In this review, recent discoveries concerning the interactions between skeletal muscle and inflammatory cells are presented. New findings clearly show a role for neutrophils in promoting muscle damage soon after muscle injury or modified use. No direct evidence is yet available to show that neutrophils play a beneficial role in muscle repair or regeneration. Macrophages have also been shown capable of promoting muscle damage in vivo and in vitro through the release of free radicals, although other findings indicate that they may also play a role in muscle repair and regeneration through growth factors and cytokine-mediated signaling. However, this role for macrophages in muscle regeneration is still not definitive; other cells present in muscle can also produce the potentially regenerative factors, and it remains to be proven whether macrophage-derived factors are essential for muscle repair or regeneration in vivo. New evidence also shows that muscle cells can release positive and negative regulators of inflammatory cell invasion, and thereby play an active role in modulating the inflammatory process. In particular, muscle-derived nitric oxide can inhibit inflammatory cell invasion of healthy muscle and protect muscle from lysis by inflammatory cells in vivo and in vitro. On the other hand, muscle-derived cytokines can signal for inflammatory cell invasion, at least in vitro. The immediate challenge for advancing our current understanding of the relationships between muscle and inflammatory cells during muscle injury and repair is to place what has been learned in vitro into the complex and dynamic in vivo environment.     

The role of cellular migration in the repair process of gastric epithelial cells.

The epithelial cells of stomach are continuously exposed to various toxic agents that may cause mucosal injury. The epithelial lining is rapidly replaced by cells that migrate from the proliferative zone of the gastric gland, to maintain the integrity of the gastric mucosa. Thus, cell migration is an essential part of the early process of gastric mucosal repair. After various forms of gastric injury, mucosal integrity is reestablished by the rapid migration of epithelial cells. However, the cellular mechanisms of the restitution remain unclear to date. In this report, we will review the role of cellular migration in the repair process of gastric epithelial cells in culture. It has been reported that hepatocyte growth factor (HGF) has the potency of acceleration of cellular repair process. In this review, we also report that HGF plays a leading role in the mucosal repair after damage by using a novel cell culture model.     

Lipid inclusions in cells and their changes during the desiccation and reactivation of yeast organisms

The formation of lipid granules in Saccharomyces cerevisiae cells was shown to begin in the exponential phase of the culture growth and to be associated with the activity of the endoplasmic reticulum. Lipid granules can be formed (1) when the endoplasmic reticulum cisterns extend and (2) when the endoplasmic reticulum membranes separate relatively small regions of the cell cytoplasm. Yeast cells contain spherosomes which differ in their structure. Lipid granules merge together upon dehydration of yeast cells. The authors discuss possible participation of these granules in the reparation of damages of the intracellular membranes.     

Time and dose dependence of pluronic bioactivity in hyperthermia-induced tumor cell death

Pluronic block copolymers have been shown to sensitize cancer cells resulting in an increased activity of antineoplastic agents. In the current study we examined a new application of Pluronic bioactivity in potentiating hyperthermia-induced cancer cell injury. DHD/K12/TRb rat adenocarcinoma cells were exposed to low-grade hyperthermia at 43 degrees C with or without Pluronic P85 or Pluronic L61. A range of Pluronic doses, pre-exposure and heat exposure durations were investigated, and the test conditions were optimized. Treatment efficacy was assessed by measurement of intracellular ATP and mitochondrial dehydrogenase activity. Both P85 and L61 in synergy with heat reduced cell viability appreciably compared to either heat or Pluronic alone. Under optimal conditions, P85 (10 mg/ml, 240 mins) combined with 15 mins heat reduced intracellular ATP to 60.1 +/- 3.5% of control, while heat alone and P85 without heat caused a negligible decrease in ATP of 1.2% and 3.8%, respectively. Similarly, cells receiving 120 mins pre-exposure of L61 (0.3 mg/ml) showed reduction in intracellular ATP to 14.1 +/- 2.1% of control. Again, heat or L61 pre-exposure alone caused a minor decrease in levels of intracellular ATP (1.5% and 4.4%, respectively). Comparable results were observed when viability was assessed by mitochondrial enzyme activity. Survival studies confirmed that the loss of viability translates to a long-term reduction in proliferative activity, particularly for L61 treated cells. Based on these results, we conclude that Pluronic is effective in improving hyperthermic cancer treatment in vitro by potentiating heat-induced cytotoxicity in a concentration and time dependent manner.     

Rapidly cooled horse spermatozoa: loss of viability is due to osmotic imbalance during thawing, not intracellular ice formation

The cellular damage that spermatozoa encounter at rapid rates of cooling has often been attributed to the formation of intracellular ice. However, no direct evidence of intracellular ice has been presented. An alternative mechanism has been proposed by Morris (2006) that cell damage is a result of an osmotic imbalance encountered during thawing. This paper examines whether intracellular ice forms during rapid cooling or if an alternative mechanism is present. Horse spermatozoa were cooled at a range of cooling rates from 0.3 to 3,000 degrees C/min in the presence of a cryoprotectant. The ultrastructure of the samples was examined by Cryo Scanning Electron Microscopy (CryoSEM) and freeze substitution, to determine whether intracellular ice formed and to examine alternative mechanisms of cell injury during rapid cooling. No intracellular ice formation was detected at any cooling rate. Differential scanning Calorimetry (DSC) was employed to examine the amount of ice formed at different rate of cooling. It is concluded that cell damage to horse spermatozoa, at cooling rates of up to 3,000 degrees C/min, is not caused by intracellular ice formation. Spermatozoa that have been cooled at high rates are subjected to an osmotic shock when they are thawed.     

Protection from heat-induced protein migration and DNA repair inhibition by cycloheximide

The mechanism by which Cycloheximide (CHM) protects cells from heat induced killing has been investigated. Cycloheximide (10 micrograms/ml) added for 2 hr before and during a 3 hour heating at 43 degrees C prevented a 40% increase of heat-induced protein accumulation in the nucleus and protected cells (0.0001 vs. 0.15 surviving fraction) from heat-induced killing. Heat-induced DNA repair inhibition was also suppressed when cells were treated with CHM in the above manner. This combination of results suggests that protein accumulation in the nucleus and inhibition of DNA repair are related and these events are associated with CHM protection from heat induced cell killing.     

The glial regenerative response to central nervous system injury is enabled by pros-notch and pros-NFκB feedback

Organisms are structurally robust, as cells accommodate changes preserving structural integrity and function. The molecular mechanisms underlying structural robustness and plasticity are poorly understood, but can be investigated by probing how cells respond to injury. Injury to the CNS induces proliferation of enwrapping glia, leading to axonal re-enwrapment and partial functional recovery. This glial regenerative response is found across species, and may reflect a common underlying genetic mechanism. Here, we show that injury to the Drosophila larval CNS induces glial proliferation, and we uncover a gene network controlling this response. It consists of the mutual maintenance between the cell cycle inhibitor Prospero (Pros) and the cell cycle activators Notch and NFκB. Together they maintain glia in the brink of dividing, they enable glial proliferation following injury, and subsequently they exert negative feedback on cell division restoring cell cycle arrest. Pros also promotes glial differentiation, resolving vacuolization, enabling debris clearance and axonal enwrapment. Disruption of this gene network prevents repair and induces tumourigenesis. Using wound area measurements across genotypes and time-lapse recordings we show that when glial proliferation and glial differentiation are abolished, both the size of the glial wound and neuropile vacuolization increase. When glial proliferation and differentiation are enabled, glial wound size decreases and injury-induced apoptosis and vacuolization are prevented. The uncovered gene network promotes regeneration of the glial lesion and neuropile repair. In the unharmed animal, it is most likely a homeostatic mechanism for structural robustness. This gene network may be of relevance to mammalian glia to promote repair upon CNS injury or disease.     

High-mobility group box 1 (HMGB1) as a master regulator of innate immunity

Damage-associated molecular patterns (DAMPs) comprise intracellular molecules characterized by the ability to reach the extracellular environment, where they prompt inflammation and tissue repair. The high-mobility box group 1 (HMGB1) protein is a prototypic DAMP and is highly conserved in evolution. HMGB1 is released upon cell and tissue necrosis and is actively produced by immune cells. Evidence suggests that HMGB1 acts as a key molecule of innate immunity, downstream of persistent tissue injury, orchestrating inflammation, stem cell recruitment/activation, and eventual tissue remodeling.     

Regulation and phylogeny of skeletal muscle regeneration

One of the most fascinating questions in regenerative biology is why some animals can regenerate injured structures while others cannot. Skeletal muscle has a remarkable capacity to regenerate even after repeated traumas, yet limited information is available on muscle repair mechanisms and how they have evolved. For decades, the main focus in the study of muscle regeneration was on muscle stem cells, however, their interaction with their progeny and stromal cells is only starting to emerge, and this is crucial for successful repair and re-establishment of homeostasis after injury. In addition, numerous murine injury models are used to investigate the regeneration process, and some can lead to discrepancies in observed phenotypes. This review addresses these issues and provides an overview of some of the main regulatory cellular and molecular players involved in skeletal muscle repair.     

Generation of functional hemangioblasts from human embryonic stem cells

Recent evidence suggests the existence of progenitor cells in adult tissues that are capable of differentiating into vascular structures as well as into all hematopoietic cell lineages. Here we describe an efficient and reproducible method for generating large numbers of these bipotential progenitors-known as hemangioblasts-from human embryonic stem (hES) cells using an in vitro differentiation system. Blast cells expressed gene signatures characteristic of hemangioblasts, and could be expanded, cryopreserved and differentiated into multiple hematopoietic lineages as well as into endothelial cells. When we injected these cells into rats with diabetes or into mice with ischemia-reperfusion injury of the retina, they localized to the site of injury in the damaged vasculature and appeared to participate in repair. Injection of the cells also reduced the mortality rate after myocardial infarction and restored blood flow in hind limb ischemia in mouse models. Our data suggest that hES-derived blast cells (hES-BCs) could be important in vascular repair.     

Coupling of endothelial injury and repair: an analysis using an in vivo experimental model

The repair of the endothelium after inflammatory injury is essential to maintaining homeostasis. The link between inflammation-induced endothelial damage and repair has not been fully characterized in vivo. We have developed a rat model to evaluate the coupling of lipopolysaccharide (LPS)-induced endothelial injury and repair. Aortic endothelium injury was analyzed by both inmunohistochemistry and flow cytometry to quantify the number of endothelial cells and the percentage of apoptotic endothelial cells. We have also identified the percentage of circulating angiogenic cells capable of repairing the damaged endothelium. Erythropoietin was administered to inhibit LPS-induced endothelial apoptosis. Loss of the normal endothelial structure was observed in the aorta of the animals treated with LPS. Eight hours after LPS administration, the number of endothelial cells decreased by 40%, returning to normal after 24 h. There was a threefold increase in the percentage of circulating angiogenic cells, which did not return to normal levels until 48 h after LPS administration. Circulating angiogenic cell levels did not change when LPS-induced endothelial damage was prevented by erythropoietin. The endothelial injury caused by inflammation activates the mobilization of circulating angiogenic cells, thus completing endothelial repair. Inflammation without endothelial injury does not trigger the mobilization of circulating angiogenic cells.     

In vitro long-term development of cultured inner ear stem cells of newborn rat

The adult mammalian auditory receptor lacks any ability to repair and/or regenerate after injury. However, the late developing cochlea still contains some stem-cell-like elements that might be used to regenerate damaged neurons and/or cells of the organ of Corti. Before their use in any application, stem cell numbers need to be amplified because they are usually rare in late developing and adult tissues. The numerous re-explant cultures required for the progressive amplification process can result in a spontaneous differentiation process. This aspect has been implicated in the tumorigenicity of stem cells when transplanted into a tissue. The aim of this study has been to determine whether cochlear stem cells can proliferate and differentiate spontaneously in long-term cultures without the addition of any factor that might influence these processes. Cochlear stem cells, which express nestin protein, were cultured in monolayers and fed with DMEM containing 5% FBS. They quickly organized themselves into typical spheres exhibiting a high proliferation rate, self-renewal property, and differentiation ability. Secondary cultures of these stem cell spheres spontaneously differentiated into neuroectodermal-like cells. The expression of nestin, glial-fibrillary-acidic protein, vimentin, and neurofilaments was evaluated to identify early differentiation. Nestin expression appeared in primary and secondary cultures. Other markers were also identified in differentiating cells. Further research might demonstrate the spontaneous differentiation of cochlear stem cells and their teratogenic probability when they are used for transplantation.     

Scanning electron microscopy of olfactory rosette in sea trout

Summary Scanning electron microscopy has been employed to study the central axis and laminae of the olfactory rosette in adult sea trout (Salmo trutta trutta L.) caught in the River Umeälven when they were homing from sea.—Both flat sides of the primary laminae are secondarily folded all over their surface. In one organ there are about 200 secondary laminae usually arranged in longitudinal, parallel ridges crossing the surface of the primary laminae. Initially they are covered with sensory epithelium, but as the folds grow they become covered with an increasing area of indifferent ciliar epithelium with bushes of cilia separated by microvilli cells and goblet cells. Parts of the central axis and primary laminae have a nonciliar indifferent epithelium. The sensory epithelium has irregularly arranged cilia. Like those of the indifferent epithelium they have uniform thickness and granulated surface. The function of laminae, secretion and cilia is discussed.The author wish to acknowledge the technical facilities and assistance in the use of the scanning electron microscope to Jeolco Stockholm office. This research was supported by grants 2389-10, 2389-11 and 2389-13 from the Swedish Natural Science Research Council.