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Kalpha yields from Ti foils irradiated with ultrashort laser pulses.

We have studied the emission of Kalpha radiation from Ti foils irradiated with ultrashort (45 fs) laser pulses. We utilized the fundamental (800 nm) light from a Ti:sapphire laser on bare foils and foils coated with a thin layer of parylene E (CH). The focusing was varied widely to give a range of intensities from approximately 10(15) - 10(19) W cm(-2). Our results show a conversion efficiency of laser to Kalpha energy of approximately 10(-4) at tight focus for both types of targets. In addition, the coated targets exhibited strong secondary peaks of conversion at large defocus, which we believe are due to modification of the extent of preformed plasma due to the dielectric nature of the plastic layer. This in turn affects the level of resonance absorption. A simple model of Kalpha production predicts a much higher conversion than seen experimentally and possible reasons for this are discussed.

Journal Article↗

Strategies to improve electrode positioning and safety in cochlear implants.

An injection-molded internal supporting rib has been produced to control the flexibility of silicone rubber encapsulated electrodes designed to electrically stimulate the auditory nerve in human subjects with severe to profound hearing loss. The rib molding dies, and molds for silicone rubber encapsulation of the electrode, were designed and machined using AutoCad and MasterCam software packages in a PC environment. After molding, the prototype plastic ribs were iteratively modified based on observations of the performance of the rib/silicone composite insert in a clear plastic model of the human scala tympani cavity. The rib-based electrodes were reliably inserted farther into these models, required less insertion force and were positioned closer to the target auditory neural elements than currently available cochlear implant electrodes. With further design improvements the injection-molded rib may also function to accurately support metal stimulating contacts and wire leads during assembly to significantly increase the manufacturing efficiency of these devices. This method to reliably control the mechanical properties of miniature implantable devices with multiple electrical leads may be valuable in other areas of biomedical device design.

Animals↗

Embryonic Purkinje cells grafted on the surface of the adult uninjured rat cerebellum migrate in the host parenchyma and induce sprouting of intact climbing fibres.

By grafting solid pieces of cerebellar anlage onto the surface of the adult rat cerebellum, we have investigated the problem of the interactions between embryonic and adult neurons in an intact brain. A few days after grafting, embryonic astrocytic processes crossed the graft--host interface and radiated into the recipient molecular layer. Several grafted Purkinje cells also migrated into the host brain along such processes as well as adult Bergmann glia. Adult climbing fibres, labelled by means of Phaseolus vulgaris leucoagglutinin (PHA-L), sprouted new collateral branches which terminated on embryonic Purkinje cells at both extra- and intraparenchymal levels. No sign of activation of host astroglia or microglia was evident in the host cerebellum in relation to these processes. Embryonic Purkinje cells which migrated into the host cerebellum developed an adult-like morphology. Intraparenchymal grafts of neocortical embryonic tissue induced conspicuous growth of host olivary axons, characterized by a pattern which was different from that observed following cerebellar grafts. By contrast, when neocortical tissue was placed onto the surface of the recipient cerebellum, graft--host interactions were limited and climbing fibre sprouting was rarely seen. These results show that (i) supernumerary Purkinje cells can penetrate and settle in the adult intact cerebellar cortex, (ii) adult climbing fibres are able to innervate these new targets in the absence of any injury or activation of non-neuronal cells of the adult brain, and (iii) in the absence of damage to the adult brain, the plasticity of adult olivary axons is specifically elicited and controlled by embryonic Purkinje cells.

Animals↗

Olivocerebellar axon regeneration and target reinnervation following dissociated Schwann cell grafts in surgically injured cerebella of adult rats.

The ability of Schwann cells to induce the regeneration of severed olivocerebellar and Purkinje cell axons across an injury up to their deafferented targets was tested by transplanting freshly dissociated cells from newborn rat sciatic nerves into surgically lesioned adult cerebella. The grafted glial cells consistently filled the lesion gap and migrated into the host parenchyma. Transected olivocerebellar axons vigorously regenerated into the graft, where their growth pattern and direction followed the arrangement of Schwann cell bundles. Although some of these axons terminated within the transplant, many of them rejoined the cerebellar parenchyma beyond the lesion. Here, their fate depended on the territory encountered. No growth occurred in the white matter. Numerous fibres penetrated into the granular layer and formed terminal branches that remained confined within this layer. A few of them, however, regenerated up to the molecular layer and formed climbing fibres on Purkinje cell dendrites. By contrast, the growth of transected Purkinje cell axons into the grafts was very poor. These results underscore the different intrinsic responsiveness of Purkinje cell and olivocerebellar axons to the growth-promoting action of Schwann cells, and show that the development and outcome of the regenerative phenomena is strongly conditioned by the spatial organization and specific features of the environmental cues encountered by the outgrowing axons along the course they follow. However, Schwann cells effectively bridge the lesion gap, induce the regeneration of olivocerebellar axons, and direct their growth up to the deafferented host cortex, where some of them succeed in reinnervating their natural targets.

Animals↗

Response of cytoskeleton of murine osteoblast cultures to two-step freezing.

Understanding the ultrastructural response of cells to the freezing process is important for designing cryopreservation strategies for cells and tissues. The cellular structures of attached cells are targets of cryopreservation-induced damage. Specific fluorescence staining was used to assess the status of the actin filaments (F-actin) of murine osteoblasts attached to hydroxyapatite discs and plastic coverslips for a two-step freezing process. The F-actin of dead cells was depolymerized and distorted in the freezing process, whereas that of live cells had little change. The results suggest that the cytoskeleton may support the robustness of cells during cryopreservation. The present study helps to investigate the damage mechanism of attached cells during the freezing process.

Actins↗

Potential role of leucine metabolism in the leucine-signaling pathway involving mTOR.

Leucine has been shown to stimulate adipose tissue protein synthesis in vivo as well as leptin secretion, protein synthesis, hyper-plastic growth, and tissue morphogenesis in in vitro experiments using freshly isolated adipocytes. Recently, others have proposed that leucine oxidation in the mitochondria may be required to activate the mammalian target of rapamycin (mTOR), the cytosolic Ser/Thr protein kinase that appears to mediate some of these effects. The first irreversible and rate-limiting step in leucine oxidation is catalyzed by the branched-chain alpha-keto acid dehydrogenase (BCKD) complex. The activity of this complex is regulated acutely by phosphorylation of the E1alpha-subunit at Ser293 (S293), which inactivates the complex. Because the alpha-keto acid of leucine regulates the activity of BCKD kinase, it has been suggested as a potential target for leucine regulation of mTOR. To study the regulation of BCKD phosphorylation and its potential link to mTOR activation, a phosphopeptide-specific antibody recognizing this site was developed and characterized. Phospho-S293 (pS293) immunoreactivity in liver corresponded closely to diet-induced changes in BCKD activity state. Immunoreactivity was also increased in TREMK-4 cells after the induction of BCKD kinase by a drug-inducible promoter. BCKD S293 phosphorylations in adipose tissue and gastrocnemius (which is mostly inactive in vivo) were similar. This suggests that BCKD complex in epididymal adipose tissue from food-deprived rats is mostly inactive (unable to oxidize leucine), as is the case in muscle. To begin to test the leucine oxidation hypothesis of mTOR activation, the dose-dependent effects of orally administered leucine on acute activation of S6K1 (an mTOR substrate) and BCKD were compared using the pS293 antibodies. Increasing doses of leucine directly correlated with increases in plasma leucine concentration. Phosphorylation of S6K1 (Thr389, the phosphorylation site leading to activation) in adipose tissue was maximal at a dose of leucine that increased plasma leucine approximately threefold. Changes in BCKD phosphorylation state required higher plasma leucine concentrations. The results seem more consistent with a role for BCKD and BCKD kinase in the activation of leucine metabolism/oxidation than in the activation of the leucine signal to mTOR.

Adipose Tissue↗

Neonatal synapse elimination in the rat submandibular ganglion: effect of retarded target growth.

1. We have studied synapse elimination in the submandibular ganglion of neonatal rats to determine the effects of retarded target growth on synaptic development. Neurons of this ganglion provide parasympathetic innervation to the submandibular and sublingual salivary glands. 2. Ligating the main salivary ducts 2-4 days after birth at a point where nerve fibers were not damaged reduces gland weight by 55% during the 2nd wk after birth and 80% by adulthood. 3. In control animals, the average number of preganglionic inputs/neuron normally declines steadily during the first few weeks after birth, before stabilizing during the 5th wk at the control adult level. Between birth and adulthood, the number of ganglionic neurons increases by 150%. 4. Ganglia from duct-ligated animals showed an acceleration in the process of synapse elimination. Input number in experimental ganglia reached the control adult level during the 3rd wk after birth. This acceleration is confined solely to ganglia that innervate the underdeveloped glands. 5. The loss of inputs was not further enhanced by prolonged target atrophy. Thus average input numbers to neurons of 5th wk or adult experimental ganglia were not different from age-matched control values. 6. No differences from control values were seen in most cases for resting potentials, input resistances, or cell size. However, the increase in neuron number was retarded in experimental animals, and the number of synapses/neuronal profile was reduced in the adult animals. 7. Thus subnormal target growth leads to an acceleration in the process of synaptic elimination in neonatal rats. This acceleration may be mediated by alterations in the level of trophic factors emanating from the target.

Age Factors↗

Regulation of synaptic depression rates in the cricket cercal sensory system.

To assess the roles of pre- and postsynaptic mechanisms in the regulation of depression, short-term synaptic depression was characterized at the synapses between sensory neurons and two interneurons in the cricket cercal sensory system. Changes in excitatory postsynaptic potential (EPSP) amplitude with repetitive stimulation at 5 and 20 Hz were quantified and fitted to the depletion model of transmitter release. The depression rates of different sensory neuron synapses on a single interneuron varied with the age of the sensory neurons such that old sensory neuron synapses depressed faster than young synapses. Although all synapses showed depression, short-term facilitation was selectively expressed only at sensory neuron synapses on one interneuron, the medial giant interneuron (MGI). These synapses showed concurrent facilitation and depression with high-frequency stimulation (100 Hz), whereas the synapses on another interneuron, 10-3, showed only depression at all stimulus frequencies. A previous study showed that the ability of a synapse to facilitate is correlated with the identity of the postsynaptic neuron. The present results indicate that depression and facilitation are regulated independently. Depression is regulated presynaptically in a manner related to sensory neuron age; whereas, facilitation is regulated by the postsynaptic target.

Animals↗

The human RC3 gene homolog, NRGN contains a thyroid hormone-responsive element located in the first intron.

NRGN is the human homolog of the neuron-specific rat RC3/neurogranin gene. This gene encodes a postsynaptic 78-amino acid protein kinase substrate that binds calmodulin in the absence of calcium, and that has been implicated in dendritic spine formation and synaptic plasticity. In the rat brain RC3 is under thyroid hormone control in specific neuronal subsets in both developing and adult animals. To evaluate whether the human gene is also a target of thyroid hormone we have searched for T3-responsive elements in NRGN cloned genomic fragments spanning the whole gene. Labeled DNA fragments were incubated with T3 receptors (T3R) and 9-cis-retinoic acid receptors and immunoprecipitated using an anti T3R antibody. A receptor-binding site was localized in the first intron, 3000 bp downstream from the origin of transcription. Footprinting analysis revealed the sequence GGATTAAATGAGGTAA, closely related to the consensus T3-responsive element of the direct repeat (DR4) type. This sequence binds the T3R-9-cis-retinoic acid receptors heterodimers, but not T3R monomers or homodimers, and is able to confer regulation by T3R and T3 when fused upstream of the NRGN or thymidine kinase promoters. The data reported in this work suggest that NRGN is a direct target of thyroid hormone in human brain, and that control of expression of this gene could underlay many of the consequences ofhypothyroidism on mental states during development as well as in adult subjects.

Animals↗

PTEN regulates Akt kinase activity in hippocampal neurons and increases their sensitivity to glutamate and apoptosis.

The tumor suppressor phosphatase PTEN can promote apoptosis of mitotic cells by inhibiting activation of the cell survival kinase Akt. PTEN is essential for normal embryonic development, PTEN expression is associated with neuronal differentiation, and deletion of PTEN in the mouse brain results in seizures, ataxia, and other abnormalities. However, the possible roles of PTEN in regulating neuronal survival are not known. We provide evidence that PTEN sensitizes hippocampal neurons to excitotoxic death in culture and in vivo. Overexpression of wild-type PTEN decreased, while a dominant-negative PTEN increased, levels of activated Akt in cultured hippocampal neurons. Wild-type PTEN promoted, while dominant-negative PTEN prevented, apoptotic death of neurons exposed to the excitatory amino acid neurotransmitter glutamate. Hippocampal neurons of mice with reduced PTEN levels were more resistant to seizure-induced death compared to wild-type littermates. These findings demonstrate a cell death function of PTEN in hippocampal neurons and identify PTEN as a potential therapeutic target for neurodegenerative disorders that involve excitotoxicity and apoptosis. The ability of PTEN to modify neuronal sensitivity to glutamate also suggests possible roles for PTEN in regulating developmental and synaptic plasticity.

Animals↗

Occupational skin diseases in Washington State, 1989 through 1993: using workers' compensation data to identify cutaneous hazards.

OBJECTIVES: This study sought to characterize occupational dermatoses and cutaneous hazards. METHODS: Workers' compensation claims filed for skin disease in the Washington State Fund were analyzed for 1989 through 1993; incidence rates for industries and employers were calculated, and cutaneous hazards associated with the highest rates were identified. RESULTS: A total of 7445 claims were filed for skin disorders, principally contact dermatitis; 675 (9.1%) involved more than 3 missed work-days. The rate of accepted skin disorder claims was 1.0 per 1000 full-time employee-years. The highest incidence rates (4.6 to 30.7 accepted claims per 1000 full-time employee-years) were in certain manufacturing industries (plastics related, concrete products, aircraft parts, sporting goods, and boat building), wholesale farm product raw materials, automotive glass replacement, and beauty shops. Seven of the 10 employers with the highest incidence rates (19.6 to 85.5 accepted claims per 1000 full-time employee-years) used fiber-reinforced plastics (composites) and exposed workers to epoxy and other resin systems associated with contact dermatitis. CONCLUSIONS: Workers' compensation data identify known and emerging workplace cutaneous hazards and show promise for targeting prevention efforts.

Dermatitis, Occupational↗

Ferroptosis in Oral Cancer: Mechanistic Insights and Clinical Prospects.

Ferroptosis, an iron-dependent form of regulated cell death characterized by lipid peroxidation, has emerged as a pivotal vulnerability in oral squamous cell carcinoma (OSCC). This review provides an overview of ferroptosis mechanisms and their implications for OSCC pathobiology and therapy. OSCC cells exhibit heightened reliance on anti-ferroptotic defenses such as GPX4, SLC7A11, FSP1, and Nrf2, and disrupting these pathways suppresses tumor growth and restores sensitivity to chemotherapy, radiotherapy, and immunotherapy. Genetic and epigenetic regulators, including p53, PER1, circ_0000140, and STARD4-AS1, critically modulate ferroptotic sensitivity, while metabolic enzymes such as ACSL4, LPCAT3, and TPI1 link ferroptosis to cellular plasticity and resistance. Preclinical studies highlight the promise of small-molecule inhibitors, repurposed agents (e.g., sorafenib, artesunate, trifluoperazine), natural compounds (e.g., piperlongumine, Evodia lepta, quercetin), and nanomedicine platforms for targeted ferroptosis induction. We further address ferroptosis within the tumor microenvironment, highlighting its immunogenic and context-dependent dual roles, and summarize genomic and transcriptomic evidence linking ferroptosis-related genes to patient prognosis. Beyond cancer, ferroptosis also contributes to non-malignant oral diseases, including pulpitis, periodontitis, and infection-associated inflammation, where inhibitors may protect tissues. Despite these advances, clinical translation is constrained by the lack of safe ferroptosis inducers and validated biomarkers. Future research should focus on developing pharmacologically viable GPX4 inhibitors, refining biomarker-driven patient stratification, and designing multimodal regimens that combine ferroptosis induction with standard therapies while preserving immune and tissue integrity. Ferroptosis therefore represents both a mechanistic framework and a translational opportunity to reshape oral oncology and broader oral disease management.

Humans↗

Segregation of presynaptic inputs on an identified target neuron in vitro: structural remodeling visualized over time.

Sensory cells of Aplysia form chemical synapses with the motor cell L7 in culture. Under certain conditions, sensory cells will also form electrical connections with each other. Sites of chemical synaptic interaction between the sensory cells and L7 are located at varicosities along sensory cell processes that overlie the main axons of L7, since these structures have been shown ultrastructurally to contain active zones. Previous studies have suggested that the distribution of sensory cell varicosities can be restricted to exclusive regions of the motor cell by the presence of other sensory cells. We wished to investigate (1) how this segregated pattern is generated over time and (2) whether electrical coupling between sensory cells has an effect on this segregated pattern. Using fluorescent dye injection and low-light video microscopy, we visualized the distribution of varicosities for each of two sensory cells growing on L7. In cases in which sensory cells are not electrically coupled, the varicosities from these two cells are spatially segregated on the target after 4 d in culture but not after 2 d in culture. Examination of the varicosity distribution of the same sensory cells on the second and third day of growth indicated both an increased rate in the elimination of varicosities from previously occupied areas and a restriction of varicosity formation in new areas of the target when a second sensory cell is present. For sensory cells that are electrically coupled, varicosities from these cells were not spatially segregated on the target even after 4 d in culture. These observations in vitro suggest that segregation of synaptic inputs by Aplysia sensory cells, which show little spontaneous activity of action potentials, can emerge over time via a process that includes both the elimination of existing sensory varicosities and the restriction of new varicosity formation. Our results also suggest that electrical connections between presynaptic cells can disrupt the segregation of their varicosities on a target, resulting in significant changes in the developing connectivity.

Animals↗

Replication of herpes simplex virus in mouse spleen cell cultures stimulated by lipopolysaccharide.

Replication of HSV was demonstrated in spleen cell cultures of D2 and several other strains of mice after prestimulation with mitogenic doses of LPS for 2 days. No viral replication occurred in unstimulated cultures or in cultures prestimulated with PHA and Con A, whereas there was some viral replication in spleen cell cultures of D2 mice after prestimulation with Poly I-C. Spleen cells of B6 mice did not support replication of HSV under any of the conditions we have tested thus far. The reasons for this defect are not clear, but it was obviously not caused by a defective lymphoproliferative response to LPS or by an active anti-viral principle elaborated by B6 spleen cells. F1 hybrids between B6 and D2 mice were capable of HSV replication to the same extent as were spleen cells of D2 mice. Several strains of both HSV-1 and HSV-2 could be replicated in D2 spleen cells cultures. Nylon column treatment of D2 spleen cells removed the ability to replicate HSV, whereas macrophage removal from the spleens by plastic adherence was without effect. Purified peritoneal exudate cells from D2 mice did not support replication of HSV. Together these data suggest that B cells activated by LPS represent the target cell of HSV replication in mouse spleen cell cultures.

Animals↗

Short-term afferent axotomy increases both strength and depression at Ia-motoneuron synapses in Rat.

Synaptic efficacy at the rat Ia-motoneuron synapse has been reported to increase in vivo, within 3 d of sectioning a single muscle nerve (). We provide an indirect test of the hypothesis that this increase is caused by altered probability of transmitter release of axotomized afferents. Experiments consisted of in vivo recording of maximal composite group I EPSPs evoked in intact rat medial gastrocnemius (MG) motoneurons by stimulation of the lateral gastrocnemius-soleus nerve (LG-S). We compared the maximal LG-S EPSP amplitude and the response to high-frequency stimulation (modulation) recorded in untreated rats, with the same measures recorded in rats that had the LG-S nerve axotomized 3 d before data collection. In confirmation of previous work, the mean amplitude of LG-S EPSPs evoked by stimulation of axotomized afferents was significantly larger than that measured in untreated rats (3.9 +/- 0. 34 and 2.3 +/- 0.19 mV, respectively). The increase in EPSP amplitude was accompanied by significantly greater negative modulation (depression) of EPSP amplitude during high-frequency stimulation (-39 +/- 4% and -53 +/- 4%, untreated and treated, respectively). Modulation would not be expected to change if the increase in EPSP amplitude was attributable solely to a greater number of afferent connections (). Therefore, the present results are consistent with the hypothesis that the initial axotomy-induced increase in synaptic efficacy occurs because of an increase in the probability of transmitter release. Furthermore, these results suggest that the probability of transmitter release at this synapse is regulated by either afferent activity and/or trophic communication with the target muscle.

Animals↗

The unitary modification rules for neural networks with excitatory and inhibitory synaptic plasticity.

The unitary Hebbian modification rules for homo-, hetero- and associative LTP and LTD of excitatory and inhibitory synaptic transmission in the neocortex and hippocampus is proposed. To provide the realization of Hebbian rule it is postulated that only synapses activated by the transmitter are modifiable. The necessary condition for the induction of heterosynaptic LTD is the convergence of homo- and heterosynaptic afferents on both the target cell and 'common' inhibitory interneuron; and modification of common inhibitory pathway efficacy. It is revealed by computational model of postsynaptic processes that in a stationary state post-tetanic synaptic efficacy does not depend on the initial efficacy but is completely defined by the amount of transmitter released during tetanization. Excitatory (inhibitory) synaptic efficacy monotonically increases (decreases) with the intracellular Ca2+ rise that is proportional to stimulation frequency enlargement. Hebbian rule, the coincidence of pre- and postsynaptic cell activity, is only necessary conditions for synaptic plasticity. Modification, such as simultaneous LTP of excitation and LTD of inhibition (LTD of excitation and LTP of inhibition) could be obtained only due to variations in pre- and/or postsynaptic activity and subsequent positive (negative) shift in the ratio between protein kinases and phosphatases in reference to prior ratio.

Calcium↗

Differential distribution of functional receptors for neuromodulators evoking short-term heterosynaptic plasticity in Aplysia sensory neurons.

Synaptic transmission and excitability in Aplysia sensory neurons (SNs) are bidirectionally modulated by 5-HT and FMRFamide. To explore the regional distribution of different functional receptors that modulate SN properties, we examined changes in synaptic efficacy and excitability with brief focal applications of the neuromodulators to different regions of SNs that have established connections with motor cell L7 in culture. Short-term changes in synaptic efficacy were evoked only when 5-HT or FMRFamide was applied to regions with SN varicosities along the surface of L7 axons. Applications to adjacent SN neurites with few varicosities in contact with L7 axons failed to evoke a significant change in synaptic efficacy. The distribution of functional receptors mediating changes in excitability differed for 5-HT and FMRFamide. Whereas excitability increases were evoked only when 5-HT was applied to SN cell bodies, excitability decreases in SNs were evoked only when FMRFamide was applied to regions along the L7 axon with SN varicosities. Without the target cell, cell bodies of SNs expressed both 5-HT and FMRFamide receptors that modulate excitability. These results indicate that functional G-protein-coupled receptors for two neuromodulators are distributed differentially along the surface of a presynaptic neuron that forms chemical connections in vitro. This differential distribution of receptors on the presynaptic neuron is regulated by a target and does not require the physical presence of neurons that release the neuromodulators.

Animals↗

Role of structural and dynamical plasticity in Sin3: the free PAH2 domain is a folded module in mSin3B.

The co-repressor Sin3 is the essential scaffold protein of the Sin3/HDAC co-repressor complex, which is recruited to the DNA by a diverse group of transcriptional repressors, targeting genes involved in the regulation of the cell cycle, proliferation and differentiation. Sin3 contains four repeats commonly denoted as paired amphipathic helix (PAH1-4) domains that provide the principal interaction surface for various repressors. Here, we present the first structure of the free state of the PAH2 domain and discuss its implications for interaction with the repressors. The unbound conformation is very similar to the conformation observed when bound to either the Mad1 or HBP1 repressor, suggesting that the PAH2 domain serves as a template that guides proper folding of the unstructured repressor. The free PAH2 domain shows micro- to millisecond conformational exchange between the folded, major state and a partially unfolded, minor state. Upon complex formation, we observe a significant decrease in fast time-scale flexibility of local regions of the protein, correlated with the formation of intermolecular contacts, and an overall decrease in the slow time-scale conformational exchange. On the basis of our data and using a multiple sequence alignment of all PAH domains, we suggest that the PAH1, PAH2 and PAH3 domains form pre-folded binding modules in full-length Sin3 like beads-on-a-string, and act as folding templates for the interaction domains of their targets.

Amino Acid Sequence↗