Physiology and molecular basis of thallium toxicity and accumulation in Arabidopsis thaliana

Thallium (Tl) is a non-essential metal mobilized through industrial processes which can lead to it entering the environment and exerting toxic effects. Plants are fundamental components of all ecosystems. Therefore, understanding the impact of Tl on plant growth and development is of great importance for assessing the potential environmental risks of Tl. Here, the responses of Arabidopsis thaliana to Tl were elucidated using physiological, genetic, and transcriptome analyses. Thallium can be absorbed by plant roots and translocated to the aerial parts, accumulating at comparable concentrations throughout plant parts. Genetic evidence supported the regulation of Tl uptake and movement by different molecular compartments within plants. Thallium primarily caused growth inhibition, oxidative stress, leaf chlorosis, and the impairment of K homeostasis. The disturbance of redox balance toward oxidative stress was supported by significant differences in the expression of genes involved in oxidative stress and antioxidant defense under Tl exposure. Reduced GSH levels in cad2-1 mutant rendered plants highly sensitive to Tl, suggesting that GSH has a prominent role in alleviating Tl-triggered oxidative responses. Thallium down-regulation of the expression of LCHII-related genes is believed to be responsible for leaf chlorosis. These findings illuminate some of the mechanisms underlying Tl toxicity at the physiological and molecular levels in plants with an eye toward the future environment management of this heavy metal.

Temporal transformation of indium speciation in rice paddy soils and spatial distribution of indium in rice rhizosphere

Indium is a potentially toxic element that could enter human food chains, including soil-rice systems. The submerged environment in rice paddy soil results in temporal and spatial variations in the chemical properties of the rice rhizosphere and bulk soils, expected to cause changes in indium's chemical speciation and consequently affect its bioavailability. Therefore, this study aimed to investigate indium speciation and fractionation in soils at different periods of rice growth under continuous submergence using X-ray absorption spectroscopy and a sequential extraction method. The predominant indium species were identified as indium-associated Fe hydroxide, and indium hydroxide and phosphate precipitates. The reductive dissolution of indium-associated Fe hydroxides led to the release of indium into the soil solution under continuous submergence of soils, and the released indium concentration decreased with time due to re-sorption and re-precipitation. Meanwhile, indium hydroxide was found to be the predominant species in rice rhizosphere using μ-X-ray absorption spectroscopy. The relative depletion of indium-associated Fe hydroxides in the rice rhizosphere was attributed to the low mobility of indium from bulk soil to rice rhizosphere and the root uptake of indium associated with Fe hydroxide around rice roots. Consequently, indium uptake by rice roots was lower during the reproductive and grain-ripening stage of rice growth. Understanding the behavior of indium will help develop a strategy to minimize uptake into crops in indium-contaminated paddy soils.

Lytic granule exocytosis at immune synapses: lessons from neuronal synapses

Regulated exocytosis is a central mechanism of cellular communication. It is not only the basis for neurotransmission and hormone release, but also plays an important role in the immune system for the release of cytokines and cytotoxic molecules. In cytotoxic T lymphocytes (CTLs), the formation of the immunological synapse is required for the delivery of the cytotoxic substances such as granzymes and perforin, which are stored in lytic granules and released via exocytosis. The molecular mechanisms of their fusion with the plasma membrane are only partially understood. In this review, we discuss the molecular players involved in the regulated exocytosis of CTL, highlighting the parallels and differences to neuronal synaptic transmission. Additionally, we examine the strengths and weaknesses of both systems to study exocytosis.

Heterozygous OT-I mice reveal that antigen-specific CD8+ T cells shift from apoptotic to necrotic killers in the elderly

Numerous alterations in CD8⁺ T cells contribute to impaired immune responses in elderly individuals. However, the discrimination between cell-intrinsic dysfunctions and microenvironmental changes is challenging. TCR transgenic OT-I mice are utilized to investigate CD8⁺ T-cell immunity, but their immunodeficient phenotype hampers their use especially in aging. Here, we demonstrate that using a heterozygous OT-I model minimizes the current limitations and provides a valuable tool to assess antigen-specific T-cell responses even at old age. We analyzed phenotypic and functional characteristics of CD8⁺ T cells from OT-I^+/+ and OT-I^+/- mice to prove the applicability of the heterozygous system. Our data reveal that OVA-activated CD8⁺ T cells from adult OT-I^+/- mice proliferate, differentiate, and exert cytolytic activity equally to their homozygous counterparts. Moreover, common age-related alterations in CD8⁺ T cells, including naive T-cell deterioration and decreased proliferative capacity, also occur in elderly OT-I^+/- mice, indicating the wide range of applications for in vivo and in vitro aging studies. We used the OT-I^+/- model to investigate cell-intrinsic alterations affecting the cytotoxic behavior of aged CD8⁺ T cells after antigen-specific in vitro activation. Time-resolved analysis of antigen-directed target cell lysis confirmed previous observations that the cytotoxic capacity of CD8⁺ T cells increases with age. Surprisingly, detailed single cell analysis revealed that transcriptional upregulation of perforin in aged CD8⁺ T cells shifts the mode of target cell death from granzyme-mediated apoptosis to rapid induction of necrosis. This unexpected capability might be beneficial or detrimental for the aging host and requires detailed evaluation.

Study of Effector CD8+ T Cell Interactions with Cortical Neurons in Response to Inflammation in Mouse Brain Slices and Neuronal Cultures

Cytotoxic CD8+ T cells contribute to neuronal damage in inflammatory and degenerative CNS disorders, such as multiple sclerosis (MS). The mechanism of cortical damage associated with CD8+ T cells is not well understood. We developed in vitro cell culture and ex vivo brain slice co-culture models of brain inflammation to study CD8+ T cell-neuron interactions. To induce inflammation, we applied T cell conditioned media, which contains a variety of cytokines, during CD8+ T cell polyclonal activation. Release of IFNγ and TNFα from co-cultures was verified by ELISA, confirming an inflammatory response. We also visualized the physical interactions between CD8+ T cells and cortical neurons using live-cell confocal imaging. The imaging revealed that T cells reduced their migration velocity and changed their migratory patterns under inflammatory conditions. CD8+ T cells increased their dwell time at neuronal soma and dendrites in response to added cytokines. These changes were seen in both the in vitro and ex vivo models. The results confirm that these in vitro and ex vivo models provide promising platforms for the study of the molecular details of neuron-immune cell interactions under inflammatory conditions, which allow high-resolution live microscopy and are readily amenable to experimental manipulation.

Separation of Single Core and Multicore Lytic Granules by Subcellular Fractionation and Immunoisolation

Subcellular fractionation is an important tool used to separate intracellular organelles, structures or proteins. Here, we describe a stepwise protocol to isolate two types of lytic granules, multicore (MCG), and single core (SCG), from primary murine CTLs. We used cell disruption by nitrogen cavitation followed by separation of organelles via discontinuous sucrose density gradient centrifugation. Immunoisolation with a Synaptobrevin 2 antibody attached to magnetic beads was then used to harvest Synaptobrevin 2 positive granules for immunoblotting, mass spectrometry, electron, and light microscopy.

Identification of distinct cytotoxic granules as the origin of supramolecular attack particles in T lymphocytes

Cytotoxic T lymphocytes (CTL) kill malignant and infected cells through the directed release of cytotoxic proteins into the immunological synapse (IS). The cytotoxic protein granzyme B (GzmB) is released in its soluble form or in supramolecular attack particles (SMAP). We utilize synaptobrevin2-mRFP knock-in mice to isolate fusogenic cytotoxic granules in an unbiased manner and visualize them alone or in degranulating CTLs. We identified two classes of fusion-competent granules, single core granules (SCG) and multi core granules (MCG), with different diameter, morphology and protein composition. Functional analyses demonstrate that both classes of granules fuse with the plasma membrane at the IS. SCG fusion releases soluble GzmB. MCGs can be labelled with the SMAP marker thrombospondin-1 and their fusion releases intact SMAPs. We propose that CTLs use SCG fusion to fill the synaptic cleft with active cytotoxic proteins instantly and parallel MCG fusion to deliver latent SMAPs for delayed killing of refractory targets.

Soil gallium speciation and resulting gallium uptake by rice plants

Gallium (Ga) is widely used in high-tech industries and is an emerging contaminant in the environment. This study aimed to determine Ga speciation in soils and Ga accumulation in rice plants (Oryza sativa L.) grown in three Ga-contaminated soils. The results showed that, among the soils, the acidic soil with a coarse texture had the highest soil Ga availability, which enhanced Ga uptake by rice roots. The Ga K-edge X-ray absorption near edge structure and sequential extraction results of the soils showed that the predominant species of Ga associated with iron hydroxides transformed to Ga(OH)₃ precipitates, and the residue fraction increased with rice-growing time, resulting in lower Ga uptake by rice roots in the second half period of rice cultivation. A large fraction of Ga was accumulated in the rice roots, with only a small portion of Ga was transferred to the shoots and then to the rice grains. This study revealed that Ga speciation in soil-rice plant systems varied during rice cultivation and determined soil Ga availability to rice plants. Gallium accumulated in rice grains is distributed homogenously in the endosperm of the grains, suggesting a potential risk to public health via the intake of rice grains harvested from Ga-contaminated paddy fields.

Differential expression of hypoxia-inducible factors related to the invasiveness of epithelial ovarian cancer

Ovarian cancer is the most lethal gynecological cancer, and it is frequently diagnosed at advanced stages, with recurrences after treatments. Treatment failure and resistance are due to hypoxia-inducible factors (HIFs) activated by cancer cells adapt to hypoxia. IGFBP3, which was previously identified as a growth/invasion/metastasis suppressor of ovarian cancer, plays a key role in inhibiting tumor angiogenesis. Although IGFBP3 can effectively downregulate tumor proliferation and vasculogenesis, its effects are only transient. Tumors enter a hypoxic state when they grow large and without blood vessels; then, the tumor cells activate HIFs to regulate cell metabolism, proliferation, and induce vasculogenesis to adapt to hypoxic stress. After IGFBP3 was transiently expressed in highly invasive ovarian cancer cell line and heterotransplant on mice, the xenograft tumors demonstrated a transient growth arrest with de-vascularization, causing tumor cell hypoxia. Tumor re-proliferation was associated with early HIF-1α and later HIF-2α activations. Both HIF-1α and HIF-2α were related to IGFBP3 expressions. In the down-expression of IGFBP3 in xenograft tumors and transfectants, HIF-2α was the major activated protein. This study suggests that HIF-2α presentation is crucial in the switching of epithelial ovarian cancer from dormancy to proliferation states. In highly invasive cells, the cancer hallmarks associated with aggressiveness could be activated to escape from the growth restriction state.

Characteristics Predicting a High Caregiver Burden in Patients with Vascular Cognitive Impairment: Using the Apriori Algorithm to Delineate the Caring Scenario

Purpose

The aim of this study was to elucidate the factors and caring scenarios associated with a moderate to severe care burden in the caregivers of patients with vascular cognitive impairment (VCI).

Patients and Methods

This cross-sectional study included 158 patients with VCI and their caregivers who were managed by the dementia collaborative care team at Changhua Christian Hospital, Taiwan. Gender, age, clinical dementia rating, walking ability, behavioral symptoms, and psychological symptoms were the variables from the patients with VCI. Age, marital status, relation to the VCI patient, education, employment status, help of key activities, type of primary care, frequency of care, ZBI (Zarit burden interview) caregiving burden, and caregiver's mood were the evaluated variables for the caregivers. The Apriori algorithm was used to identify the attributes that resulted in different caregiving burdens from a comprehensive viewpoint of both VCI patients and their caregivers.

Results

A total of 1193 rules were identified with 1134 rules belonging to caregivers with a mild to moderate burden and 59 rules belonging to caregivers with a moderate to severe burden. Seven general rules were created based on a summary of these 59 rules. The results showed that an employed female caregiver who was taking care of her husband alone for ≥6 days per week, and who was helping with all key activities was likely to experience a moderate to severe burden when the patient had VCI. Moreover, if the caregiver had a relatively low education level and expressed an abnormal mood during the assessment, this increased the likelihood of the caregiver having a moderate to severe burden.

Conclusion

The caregiver's gender, relation to the care recipient, education level, mood status, employment status, and care loading were associated with a higher burden of care for caregivers of patients with VCI. Therefore, a dementia care team should provide personalized training for caregivers about the disease, care skills for specific behaviors and psychological symptoms of dementia (BPSD), and strategies to cope with their own feelings. Caregivers should also be referred to appropriate social resources, such as support groups or respite care.

Indium Uptake and Accumulation by Rice and Wheat and Health Risk Associated with Their Consumption

The increasing use of indium in high-tech industries has inevitably caused its release into the environment. However, knowledge of its environmental fate has been very limited so far. This study investigates the indium uptake and accumulation by two staple crops, rice (Oryza sativa L.) and wheat (Triticum aestivum L.), and evaluates potential risks associated with their consumption. Rice and wheat were grown on three kinds of soil, including acidic soils spiked with a high indium concentration (1.0 mmol kg^-1), which is considered the worst-case scenario, because high soil acidity promotes indium bioavailability. The results revealed that a large portion of soil indium was associated with iron hydroxides, even in acidic soils. Indium precipitates in soils resulted in relatively low availability at the plant root site. Most absorbed indium accumulated at the roots, with only a tiny portion reaching the grains. The corresponding Hazard Quotient indicated no adverse effects on human health. Due to the low translocation of indium from soil to grain, the consumption of rice and wheat grains harvested from indium-contaminated soils may pose an insignificant risk to human health. Further field studies are necessary to better elucidate the risks associated with consuming crops grown in indium-contaminated soils.

Studying the biology of cytotoxic T lymphocytes in vivo with a fluorescent granzyme B-mTFP knock-in mouse

Understanding T cell function in vivo is of key importance for basic and translational immunology alike. To study T cells in vivo, we developed a new knock-in mouse line, which expresses a fusion protein of granzyme B, a key component of cytotoxic granules involved in T cell-mediated target cell-killing, and monomeric teal fluorescent protein from the endogenous Gzmb locus. Homozygous knock-ins, which are viable and fertile, have cytotoxic T lymphocytes with endogeneously fluorescent cytotoxic granules but wild-type-like killing capacity. Expression of the fluorescent fusion protein allows quantitative analyses of cytotoxic granule maturation, transport and fusion in vitro with super-resolution imaging techniques, and two-photon microscopy in living knock-ins enables the visualization of tissue rejection through individual target cell-killing events in vivo. Thus, the new mouse line is an ideal tool to study cytotoxic T lymphocyte biology and to optimize personalized immunotherapy in cancer treatment.

Engineering a Ga-Gradient by One-Step Sputtering to Achieve Over 15% Efficiency of Cu(In,Ga)Se2 Flexible Solar Cells without Post-selenization

A one-step sputtering process using a quaternary target has been demonstrated to be a simple route to form Cu(In,Ga)Se₂ (CIGSe) absorber without post-selenization; however, the lack of a Ga-grading structure in the CIGSe absorber confines its efficiency. Here, we demonstrate a one-step cosputtering process to control the Ga profile in the CIGSe absorber on flexible stainless steel substrates. Special attention was paid to the formation of second phases and their effects on the cell performance. Although the normal Ga-grading and efficiency enhancement could be achieved by cosputtering of CIGSe and Ga₂Se₃ targets, high-energy ion bombardment during the sputtering process might cause the decomposition of the Ga₂Se₃ target, leading to the formation of Ga₂O₃ in the CIGSe absorber, which gradually degraded the device performance. We replaced the Ga₂Se₃ target with a stoichiometric CuGaSe₂ target for cosputtering, which can further enhance the cell efficiency due to the elimination of Ga₂O₃. However, when the Ga content at the back side of CIGSe is further increased by raising the deposition power of the CuGaSe₂ target, the phase separation of CuGaSe₂ may take place, resulting in the formation of Cu_2-XSe and CuGaSe₂ at the back side of the CIGSe absorber; therefore, the recombination at the back side is increased. By cosputtering a CIGSe target with a Cu-deficient CuGaSe₂ target, we can suppress the formation of second phases and achieve designable normal grading, leading to the highest efficiency of 15.63% without post-selenization on flexible substrates.

A Ib/II study of the combination of lenvatinib (L) and eribulin (E) in advanced liposarcoma (LPS) and leiomyosarcoma (LMS) (LEADER)

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Background: For advanced LPS and LMS, the two most common histologies in soft tissue sarcoma, there are limited treatment options that readily balance efficacy and toxicity. Patients (pts) treated with E had an improved median overall survival (OS) in a phase III randomized study compared to dacarbazine but with an unsatisfactory 4% objective response rate (ORR). Early studies of L, a multi-targeted anti-angiogenic inhibitor, had suggested efficacy in sarcoma pts. We hypothesized that the combination of anti-angiogenic agent and chemotherapy could potentiate treatment benefit and aimed to explore the safety and efficacy of L + E in advanced LMS and LPS. Methods: LEADER was a single-arm phase Ib/II study for advanced adult LMS and LPS pts who had received no more than 2 lines of systemic chemotherapy. The phase Ib part (starting dose: L 18mg/day, E 1.1mg/m2) had been reported and the recommended phase 2 dose (RP2D) was determined at L 14mg/day and E 1.1mg/m2 D1, D8 every 21 days. The primary endpoint of the phase II part was ORR by RECIST 1.1, secondary endpoints included ORR by Choi criteria, progression-free survival (PFS), 6-month PFS rate, and OS. With α = 0.05 and 80% power, the pts needed for stage I and total of the Simon 2-stage design was 13 and 27 pts, respectively. Results: As of Jan 22, 2020, 20 pts (F/M 13/7) had been treated with at least one cycle of L + E; 14 were LMS (5 uterine, 9 non-uterine) and 6 were LPS (4 dedifferentiated, 2 myxoid round cell). The median age was 51 (range 29-73); the median lines of treatment(s) received before enrollment was 1 (range 0-3). 18 pts were evaluable for primary endpoint: the ORR by RECIST 1.1 was 27 % (5/18) (95% CI 10-53%). The ORR by Choi criteria was 67 % (12/18) (95% CI 41-87%). With 8 PFS events, the median PFS and 6-month PFS rate was 56 weeks (95% CI 25-not reached) and 72%, respectively. There were no OS events. The ORRs by RECIST 1.1 between different L starting doses were not significantly different (18mg 33% (2/6) vs 14mg 25% (3/12), p = 0.7). 15 pts experienced at-least one grade (gr) 3 or 4 adverse event (AE); gr 3 or 4 AEs occurred in > 1 pts included (% of phase Ib, % of phase II pts) hypertension (n = 4) (67%, 0%); hand-foot-syndrome (n = 4) (50%, 7%), proteinuria (n = 3) (0%, 25%), febrile neutropenia (n = 2) (17% vs 5%), neutropenia (n = 6) (50% vs 25%). The RP2D was associated with overall lower gr3/4 AEs except for proteinuria. Conclusions: L + E had shown promising efficacy in advanced LMS and LPS. L at 14mg/day had a better AE profile without compromising activity. The exploratory biomarker study of LEADER is ongoing. Clinical trial information: NCT03526679 .

In vivo visualization of immune responses during rejection of allogeneic tissue in the anterior eye chamber

The anterior chamber of the eye (ACE) was recently described as a novel imaging site in diabetes research by observing transplanted pancreatic islet activity in the eye of a living animal. The ACE technology is ideally suited for non-invasive and longitudinal in vivo imaging. We take advantage of the ACE window to observe immune responses, especially allorejection of islet cells by cytotoxic T lymphocytes. We transplant pancreatic islets from DBA/1J mice into C57BL/6 recipient knock-in mouse which endogenously express a fluorescent protein (GzmB-mTFP or Bonzo) in T cells. We follow the onset of the rejection after vascularization on islets, when immune cells start to infiltrate into ACE, until the end of the rejection process where the islets are cleaned up for roughly a month by repetitive two-photon microscopy. We find that T cells show less migration velocity on islets of foreign mice than on autologous tissue, indicating T cell activation and recognition on the islets. Interestingly, the temporal infiltration pattern of T cells during the rejection process is precisely regulated, showing enrichment of CD4+ T cells on the islets before arrival of CD8+ T cells in histological studies. We use the ACE platform as a more comprehensive environment to study immune response and focus on T cell killing. We aim to understand the mechanism and regulation of T cell-mediated killing in vivo and to further investigate the killing in gene-deficient mice (i.e. munc13-4 and perforin) that resemble to severe human immune disease.

Role of V-ATPase a3-Subunit in Mouse CTL Function

CTLs release cytotoxic proteins such as granzymes and perforin through fusion of cytotoxic granules (CG) at the target cell interface, the immune synapse, to kill virus-infected and tumorigenic target cells. A characteristic feature of these granules is their acidic pH inside the granule lumen, which is required to process precursors of granzymes and perforin to their mature form. However, the role of acidic pH in CG maturation, transport, and fusion is not understood. We demonstrate in primary murine CTLs that the a3-subunit of the vacuolar-type (H⁺)-adenosine triphosphatase is required for establishing a luminal pH of 6.1 inside CG using ClopHensorN(Q69M), a newly generated CG-specific pH indicator. Knockdown of the a3-subunit resulted in a significantly reduced killing of target cells and a >50% reduction in CG fusion in total internal reflection fluorescence microscopy, which was caused by a reduced number of CG at the immune synapse. Superresolution microscopy revealed a reduced interaction of CG with the microtubule network upon a3-subunit knockdown. Finally, we find by electron and structured illumination microscopy that knockdown of the a3-subunit altered the diameter and density of individual CG, whereas the number of CG per CTL was unaffected. We conclude that the a3-subunit of the vacuolar adenosine triphosphatase is not only responsible for the acidification of CG, but also contributes to the maturation and efficient transport of the CG to the immune synapse.

Assessment of indium toxicity to the model plant Arabidopsis

The use of indium in semiconductor products has increased markedly in recent years. The release of indium into the ecosystem is inevitable. Under such circumstances, effective and accurate assessment of indium risk is important. An indispensable aspect of indium risk assessment is to understand the interactions of indium with plants, which are fundamental components of all ecosystems. Physiological responses of Arabidopsis thaliana exposed to indium were investigated by monitoring toxic effects, accumulation and speciation of indium in the plant. Indium can be taken up by plants and is accumulated mainly in roots. Limited indium root-to-shoot translocation occurs because of immobilization of indium in the root intercellular space and blockage of indium by the Casparian band in the endodermis. Indium caused stunted growth, oxidative stress, anthocyanization and unbalanced phosphorus nutrition. Indium jeopardizes phosphate uptake and translocation by inhibiting the accumulation of phosphate transporters PHOSPHATE TRANSPORTER1 (PHT1;1/4), responsible for phosphate uptake, and PHOSPHATE1 (PHO1), responsible for phosphate xylem loading. Organic acid secretion is stimulated by indium exposure. Secreted citrate could function as a potential detoxifier to lower indium uptake. Our findings provide insights into the potential fate and effects of indium in plants and will aid the evaluation of risks with indium contamination.

S-Nitrosoglutathione works downstream of nitric oxide to mediate iron-deficiency signaling in Arabidopsis

Iron (Fe) is essential for plant growth and development. Knowledge of Fe signaling, from the beginning of perception to activation of the uptake process, is critical for crop improvement. Here, by using chemical screening, we identified a small molecule 3-amino-N-(3-methylphenyl)thieno[2,3-b]pyridine-2-carboxamide named R7 ('R' denoting repressor of IRON-REGULATED TRANSPORTER 1), that modulates Fe homeostasis of Arabidopsis. R7 treatment led to reduced Fe levels in plants, thus causing severe chlorosis under Fe deficiency. Expression analysis of central transcription factors, FER-LIKE IRON DEFICIENCY INDUCED TRANSCRIPTION FACTOR (FIT) and subgroup Ib basic helix-loop-helix (Ib bHLH) genes bHLH38/39/100/101, revealed that R7 targets the FIT-dependent transcriptional pathway. Exogenously supplying S-nitrosoglutathione (GSNO), but not other nitric oxide (NO) donors sodium nitroprusside (SNP) and S-nitroso-N-acetyl-dl-penicillamine (SANP), alleviated the inhibitory effects of R7 on Fe homeostasis. R7 did not inhibit cellular levels of NO or glutathione but decreased GSNO level in roots. We demonstrate that NO is involved in regulating not only the FIT transcriptional network but also the Ib bHLH networks. In addition, GSNO, from S-nitrosylation of glutathione, specifically mediates the Fe-starvation signal to FIT, which is distinct from the NO to Ib bHLH signal. Our work dissects the molecular connection between NO and the Fe-starvation response. We present a new signaling route whereby GSNO acts downstream of NO to trigger the Fe-deficiency response in Arabidopsis.

Cytotoxic granule endocytosis depends on the Flower protein

Cytotoxic T lymphocytes (CTLs) kill target cells by the regulated release of cytotoxic substances from granules at the immunological synapse. To kill multiple target cells, CTLs use endocytosis of membrane components of cytotoxic granules. We studied the potential calcium dependence of endocytosis in mouse CTLs on Flower, which mediates the calcium dependence of synaptic vesicle endocytosis in Drosophila melanogaster Flower is predominantly localized on intracellular vesicles that move to the synapse on target cell contact. Endocytosis is entirely blocked at an early stage in Flower-deficient CTLs and is rescued to wild-type level by reintroducing Flower or by raising extracellular calcium. A Flower mutant lacking binding sites for the endocytic adaptor AP-2 proteins fails to rescue endocytosis, indicating that Flower interacts with proteins of the endocytic machinery to mediate granule endocytosis. Thus, our data identify Flower as a key protein mediating granule endocytosis.

Effect of Gallium Exposure in Arabidopsis thaliana is Similar to Aluminum Stress

Although gallium (Ga) is a rare element, it is widely used in semiconductor devices. Ga contamination of the environment has been found in semiconductor-producing countries. Here, the physiological and molecular impacts of Ga in the model plant Arabidopsis thaliana were investigated in medium culture. The primary symptom of Ga toxicity is inhibition of root growth. The increased production of malondialdehyde (MDA) suggests that Ga stress could cause oxidative damage in plants. Roots were the main Ga accumulating sites. The distinctive Ga granules were deposited within the intercellular space in roots. The granules are Ga(OH)₃ precipitation, which indicates immobilization or limited translocation of Ga in A. thaliana. Ga stress induces root secretion of organic acids such as citrate and malate. The expression of the transporters AtALMT and AtMATE, responsible for citrate and malate secretion, respectively, were elevated under Ga stress, so the secretion may play a role in the resistance. Indeed, supplying exogenous citrate significantly enhanced Ga tolerance. The overall response to Ga exposure in A. thaliana is highly similar to that with aluminum stress. Our findings provide information for risk assessment in Ga-contaminated soil.

Preparing the lethal hit: interplay between exo- and endocytic pathways in cytotoxic T lymphocytes

Cytotoxic T lymphocytes patrol our body in search for infected cells which they kill through the release of cytotoxic substances contained in cytotoxic granules. The fusion of cytotoxic granules occurs at a specially formed contact site, the immunological synapse, and is tightly controlled to ensure specificity. In this review, we discuss the contribution of two intracellular compartments, endosomes and cytotoxic granules, to the formation, function and disassembly of the immunological synapse. We highlight a recently proposed sequential process of fusion events at the IS upon target cell recognition. First, recycling endosomes fuse with the plasma membrane to deliver cargo required for the docking of cytotoxic granules. Second, cytotoxic granules arrive and fuse upon docking in a SNARE-dependent manner. Following fusion, membrane components of the cytotoxic granule are retrieved through endocytosis to ensure the fast, efficient serial killing of target cells that is characteristic of cytotoxic T lymphocytes.

Endocytosis of Cytotoxic Granules Is Essential for Multiple Killing of Target Cells by T Lymphocytes

CTLs are serial killers that kill multiple target cells via exocytosis of cytotoxic granules (CGs). CG exocytosis is tightly regulated and has been investigated in great detail; however, whether CG proteins are endocytosed following exocytosis and contribute to serial killing remains unknown. By using primary CTLs derived from a knock-in mouse of the CG membrane protein Synaptobrevin2, we show that CGs are endocytosed in a clathrin- and dynamin-dependent manner. Following acidification, endocytosed CGs are recycled through early and late, but not recycling endosomes. CGs are refilled with granzyme B at the late endosome stage and polarize to subsequent synapses formed between the CTL and new target cells. Importantly, inhibiting CG endocytosis in CTLs results in a significant reduction of their cytotoxic activity. Thus, our data demonstrate that continuous endocytosis of CG membrane proteins is a prerequisite for efficient serial killing of CTLs and identify key events in this process.

Calcium-dependence of cytotoxic granule endocytosis depends on the Flower protein

Cytotoxic T lymphocytes (CTLs) kill their targets by secreting perforin and granzymes from cytotoxic granules (CGs) at the interface between CTL and target cells, the immunological synapse (IS). Retrieval of membrane proteins at the IS plays a crucial role in CTL effector function by impacting the serial killing ability of CTLs. However, the cellular and molecular mechanism of CG endocytosis is largely unknown. In neuronal synapses, it has been shown that calcium influx is instrumental to trigger endocytosis, but the identity of calcium channel remains unclear. Flower protein has been reported as a potential candidate to regulate synaptic endocytosis in drosophila. We investigated a potential calcium-dependence of CG endocytosis and whether Flower plays a role in this process. We first confirmed that Flower protein is expressed in WT mouse CD8+ CTLs by western blot. We then generated Flower-deficient mice to further study Flower function. While we observed no change of degranulation and CG secretion in Flower-deficient CTLs, CG endocytosis at the IS was entirely blocked upon target cell contact. Re-introduction of Flower protein or elevation of extracellular calcium rescued the endocytosis defect in Flower-deficient CTLs. Interestingly, live imaging data showed that Flower localizes on intracellular vesicles which polarize to the IS upon target cell contact. We conclude from our data that endocytosis of CGs is calcium-dependent and that the Flower protein is providing the required calcium, probably through release from intracellular organelles.

Endocytosis of cytotoxic granules in CD8 T lymphocytes is required for multiple killing of target cells (IRM14P.448)

Cytotoxic (CD8+) T lymphocytes (CTLs) eliminate tumorigenic and virus-infected target cells by releasing the contents of cytotoxic granules (CGs) at the immunological synapse. Even though CTLs have only a limited number of pre-existing fusogenic CGs, they can efficiently kill multiple target cells upon activation. We therefore hypothesized that, following CG fusion, the remaining components are recycled and subsequently refilled with cytotoxic substances to become available for the next round of fusion, thus enabling efficient multiple killing. We visualized endogenous CGs and their recycling in real-time in CTLs from synaptobrevin2-mRFP knock-in mice by fluorescently-labeled anti-RFP antibodies. We found that endocytosis (recycling) of CGs was blocked by Dynasore, an inhibitor of dynamin. Additionally, clathrin was colocalized with endocytosing CGs at the plasma membrane following dynasore pretreatment. Thus, endocytosis of CGs is clathrin- and dynamin-dependent. Importantly, although CTLs pre-treated with Dynasore showed no immediate effect on CG exocytosis, they exhibited a 50% deficiency in killing target cells after 2 hours of incubation. Our data strongly suggest that recycling of CGs plays an important role in CTLs for executing multiple killing of target cells.

A novel anabolic agent: a simvastatin analogue without HMG-CoA reductase inhibitory activity

For the first time, structural information regarding the role of simvastatin in bone anabolism is described, and a bone-specific statin is introduced. Polyaspartate-conjugated simvastatin was synthesized by solid-phase synthesis with the assistance of microwave irradiation. It displays significant bone targeting and bone formation with less toxicity than simvastatin.

In the crosshairs: investigating lytic granules by high-resolution microscopy and electrophysiology

Cytotoxic T lymphocytes (CTLs) form an integral part of the adaptive immune system. Their main function is to eliminate bacteria- and virus-infected target cells by releasing perforin and granzymes (the lethal hit) contained within lytic granules (LGs), at the CTL-target-cell interface [the immunological synapse (IS)]. The formation of the IS as well as the final events at the IS leading to target-cell death are both highly complex and dynamic processes. In this review we highlight and discuss three high-resolution techniques that have proven invaluable in the effort to decipher key features of the mechanism of CTL effector function and in particular lytic granule maturation and fusion. Correlative light and electron microscopy allows the correlation between organelle morphology and localization of particular proteins, while total internal reflection fluorescence microscopy (TIRFM) enables the study of lytic granule dynamics at the IS in real time. The combination of TIRFM with patch-clamp membrane capacitance measurements finally provides a tool to quantify the size of fusing LGs at the IS.

Protective effects of Ginkgo biloba, Panax ginseng, and Schizandra chinensis extract on liver injury in rats

This study investigated the effects of the combined extracts of Ginkgo biloba, Panax ginseng, and Schizandra chinensis at different doses on hepatic antioxidant status and fibrosis in rats with carbon tetrachloride (CCl4)-induced liver injury. Male Sprague-Dawley rats (n = 8-12 per group) were divided into the control, CCl4, CCl4 + silymarin (0.35%), CCl4 + low-dose herbal extract (0.24% of Ginkgo biloba, Panax ginseng, and Schizandra chinensis extract at 1:1:1; LE), and CCl4 + high-dose herbal extract (1.20% of the same herbal extract; HE) groups. Silymarin or herbal extract was orally given to rats a week before chronic intraperitoneal injection with CCl4 for 6 weeks. The pathological results showed that herbal extract suppressed hepatic bile duct proliferation, and low-dose herbal extract inhibited liver fibrosis. Hepatic superoxide dismutase (SOD) activity was lower in the CCl4 group, but there was no difference in the silymarin or herbal extract treated groups compared to the control group. Hepatic catalase activity and the ratio of reduced to oxidized glutathione were significantly higher (p < 0.05) in the HE group than those in the CCl4 group. Silymarin and herbal extract reversed the impaired hepatic total antioxidant status (p < 0.05). Herbal extract partially reduced the elevated hepatic lipid peroxides. Hepatic transforming growth factor-beta1 (TGF-beta1) level decreased significantly (p < 0.05) in the LE group. Therefore, high-dose herbal extract improved hepatic antioxidant capacity through enhancing catalase activity and glutathione redox status, whereas low-dose herbal extract inhibited liver fibrosis through decreasing hepatic TGF-beta1 level in rats with CCl4-induced liver injury.

Angular distribution of polarized photon-pairs in a scattering medium with a Zeeman laser scanning confocal microscope

A novel confocal microscope designed for use with turbid media is proposed. We use a Zeeman laser as the light source. Based on the properties of two-frequency polarized photon-pairs and the common-path feature of polarized photon-pairs with heterodyne detection employed in the proposed confocal microscope, three gatings (spatial filtering gating, polarization gating and spatial coherence gating) are thus simultaneously incorporated in the microscope. Experimental results for the angular distribution of polarized photon-pairs in a scattering medium indicate that polarization gating and spatial coherence gating preclude the detection of multiply scattered photons, whereas the pinhole selects the least scattered photon-pairs. Thus, better performance for axial resolution than can be obtained with a conventional confocal microscope is demonstrated experimentally. In addition, the proposed microscope is able to either look deeper into a turbid medium or work with a denser medium; furthermore, the axial resolution is improved.

Thin-plate spline (TPS) graphical analysis of the mandible on cephalometric radiographs

We describe two cases of Class III malocclusion with and without orthodontic treatment. A thin-plate spline (TPS) analysis of lateral cephalometric radiographs was used to visualize transformations of the mandible. The actual sites of mandibular skeletal change are not detectable with conventional cephalometric analysis. These case analyses indicate that specific patterns of mandibular transformation are associated with Class III malocclusion with or without orthopaedic therapy, and visualization of these deformations is feasible using TPS graphical analysis.

Product ion studies of diastereomeric benzo[ghi]fluoranthene tetraols by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry and post-source decay

The product ion formation characteristics of the four diastereomeric tetrahydroxy benzo[ghi]fluoranthene compounds formed by hydrolysis of the syn and anti diastereomers of trans-3,4-dihydroxy-5,5a-epoxy-3,4,5,5a-tetrahydrobenzo[ghi]fluoranthene are studied using matrix-assisted laser desorption/ionization and post-source decay (PSD) to determine a correlation between the fragmentation characteristics of these tetraols and the structures of the diol-epoxide diastereomers from which they are hydrolyzed. The tetraols formed by the trans ring opening of the diol epoxides during hydrolysis yield product ion spectra specific for the syn and anti configurations of their precursor diol epoxides. All four diastereomeric tetraols form product ions by the losses of one and/or two water molecules in varying proportions when lithium-cationized molecule ions (m/z 301) are selected for PSD product ion analysis. The differences in the PSD spectra of these four Li+-cationized molecules are rationalized in terms of a water loss mechanism that involves the 1,2 elimination of a hydrogen atom and hydroxyl group that are cis with respect to each other on adjacent carbons.

Group learning factors in a problem-based course in oral radiology

OBJECTIVES

To assess the development of group dynamics in students who participated in a problem-based learning (PBL) course in oral radiology and to evaluate the influence of the facilitators' experience.

METHODS

At the beginning and end of the course, students in three consecutive years (1997, 1998 and 1999) responded to a group learning factor questionnaire designed to measure group dynamics (engagement, interpersonal relationships, lack of commitment and disruptive behaviour, interpersonal learning and self-presentation). The answers were analysed with paired t-test and the effects of the facilitator's seniority, expertise in oral radiology, experience of PBL and single or rotating facilitators assessed.

RESULTS

Most groups in the three years reported above average group dynamic scores. There were significant changes in group dynamics. In the 1997 class, interpersonal relationships improved (P=0.014). In the 1998 class, interpersonal learning (P=0.021) and engagement (P=0.009) increased significantly, while disruptive behaviour decreased (P=0.031). In the 1999 class, lack of commitment and disruptive behaviour decreased (P=0.014). Groups led by a junior faculty member with no previous experience of PBL show less commitment and more disruptive behaviour.

CONCLUSIONS

More commitment and less disruptive behaviour and improved engagement, interpersonal relationships and self-presentation were found in a PBL course in oral radiology. Facilitators should have prior exposure to PBL to avoid disruptive behaviour among the students.

Effects of Nd:YAG laser irradiation on cultured human gingival fibroblasts

BACKGROUND AND OBJECTIVE

The Nd:YAG laser has been proposed to apply in minor soft tissue surgery, including various periodontal procedures. However, little information is available regarding the direct effect of Nd:YAG laser on gingival fibroblasts, which play an important role in the early healing processes of periodontal repair.

STUDY DESIGN/MATERIALS AND METHODS

Nd:YAG laser irradiation was performed in pulsed mode on human gingival fibroblasts, which was derived from healthy human gingiva by an explant method. The size of laser diode was 400 microm in diameter. The parameters in laser delivery were pulse energy (50-150 mJ), power output (1.0-3.0 W), pulse rate (10-30 pps), and fixed duration of irradiation (10 seconds). The cell cultures were analysed by cytomorphologic examination under phase-contrast and scanning electron microscope. The vitality was also examined with the help of MTT staining.

RESULTS

The area of laser damage on cell culture was circular in shape, with diameter beyond the size of laser diode. By scanning electron microscopy, we observed the cellular damage of cultured gingival fibroblasts induced by Nd:YAG laser irradiation, comparable with the progressive increased power settings. The cytomorphologic changes ranged from disappearance of cellular boundary, loss of identifiable cellular nucleus, and finally cell contraction and vacuolization. Significant decrease in cellular vitality (14% approximately 44%) after laser treatment with irradiation distance of nearly contact was noted. However, 2 mm defocusing irradiation with the same power settings did not significantly decrease cellular vitality.

CONCLUSION

Our study demonstrated the cell damaging effects of Nd:YAG laser, ranging from degeneratively cytomorphologic change to cell death, on the cultured human gingival fibroblasts. It provided the dentist a chance to understand the potential hazard of laser application in periodontal treatment. If the energy output is enough for the clinical purposes, Nd:YAG laser with lower pulse energy and corresponding pulse rate should be selected to minimize the damage on adjacent soft tissue.

Correlation of cervical vertebra maturation with hand-wrist maturation in children

The purpose of this study was to evaluate the reliability of cervical vertebra maturation as an indicator of skeletal age during the circumpubertal period. This was determined by correlating cervical vertebra maturation to hand-wrist maturation. The vertebral skeletal age was assessed using lateral cephalometric radiographs according to maturity indicators modified from Lamparski. The hand-wrist skeletal age was evaluated in radiographs with the system developed by Fishman. The sample consisted of 503 subjects (244 boys and 259 girls), aged 8 through 18 years. The Spearman rank correlation coefficients and Wilcoxon sign rank test showed that a statistically significant relationship existed between the two assessments. Both the intra- and inter-judge tests of reliability displayed no significant differences. The results of this study indicate that skeletal age assessment made from the maturational changes of cervical vertebrae were reliable, reproducible and valid.

Comparison of landmark identification in traditional versus computer-aided digital cephalometry

The aim of this study was to assess landmark identification on digital images in comparison with those obtained from original radiographs. Ten cephalometric radiographs were selected randomly. Seven orthodontic residents identified 19 cephalometric landmarks on both the original radiographs and the digital images. To assess the concordance between landmarks identified on the original radiographs and on their digital counterparts, the x, y coordinates for each landmark in the 2 modalities were transformed with the identical references. The placement differences for 19 landmarks between 2 methods were calculated and their components in horizontal and vertical directions were analyzed respectively. Multivariate analysis of variance showed that the "cephalometric radiograph" and "landmark" variation had greater influence than that from "method" (landmark identification on digital / original radiograph). It was also noted that the differences of landmark identification between original radiographs and their digital counterparts were statistically significant. The landmarks with significant differences of horizontal component on the x-axis were Me, Gn, ANS, PNS, LIA. The differences were generally under 1 mm with the exception of Or, Me, PNS, LIA. The landmarks with significant differences of vertical component on the y-axis were Po, Or, Gn. The inter-observer error for each landmark in digital images was generally larger than that in the original radiographs. However, statistically significant differences of inter-observer errors between 2 modalities were only found for 4 of the 19 landmarks. These 4 landmarks, Po, Ar, ANS, and UM, should be scrutinized more carefully during potential applications of digital cephalometry.

The NLM Indexing Initiative

The objective of NLM's Indexing Initiative (IND) is to investigate methods whereby automated indexing methods partially or completely substitute for current indexing practices. The project will be considered a success if methods can be designed and implemented that result in retrieval performance that is equal to or better than the retrieval performance of systems based principally on humanly assigned index terms. We describe the current state of the project and discuss our plans for the future.

The response of cAMP and DNA synthesis in rat osteosarcoma cells to mechanically deformed culture dishes

The purpose of this research was to document the biochemical response of rat osteosarcoma cells (ROS 17/2.8) to mechanical stress in vitro. The influence of mechanical stress on ROS 17/2.8 cells was studied using a stress application device. Briefly, the device was fabricated by bonding an orthodontic expansion screw outside the bottom of a plastic culture dish with self-curing acrylic resin. Irreversible deformation of the culture dish was produced by activating an expansion screw. The resulting mechanical stress was transferred to the cells which attached to the culture dish. The response in terms of cyclic adenosine monophosphate (cAMP) of ROS 17/2.8 cells to mechanical stress was measured using a competitive protein-binding method. The effect of mechanical stress on cellular growth was assessed through the incorporation of 3H-thymidine after different periods of mechanical stress application. The results revealed that mechanical stress could increase the production of cAMP in ROS 17/2.8 cells at an early phase after stress stimulation. This change in the cAMP level was dependent on the duration of stress application, and the maximal response occurred when the mechanical stress was applied for one hour. Although the cellular incorporation of 3H-thymidine decreased 40-60% in ROS 17/2.8 cells subjected to mechanical stress for 1 hour, this reaction recovered from the inhibition effect to 80-85% of the baseline when the mechanical stress lasted for 24 hours. The observations in this study indicate that mechanical stress stimulates the production of cAMP and inhibits the 3H-thymidine incorporation of ROS 17/2.8 cells at an early phase of stress application.

Beyond synonymy: exploiting the UMLS semantics in mapping vocabularies

The Unified Medical Language System (UMLS) contains semantic information about terms from various sources, each concept can be understood and located by its relationships to other concepts: this is a result of the organizing principle of semantic locality. We describe a method in which the semantic relationships between concepts are used to map concepts from different vocabularies in the UMLS. Applied to mapping concepts to MeSH, this method is able to map 50 to 65% of the non-MeSH concepts to MeSH. A manual review of the mapping shows a relevance rate of 61%. Causes of failure include a lack of consistently represented relationships in the UMLS, and some inconsistencies in the categorization of the concepts. The limits of this method are discussed, as well as possible adaptations for other uses.

Observation of bolus position with standardized test foods and fluoroscopic technique

Sugar and agar balls containing barium were made for the fluoroscopic observation of the bolus position during habitual side chewing in 13 adult males (aged from 20 to 28 years) who had a complete dentition and healthy masticatory system. The test foods had constant size, shape, weight and known hardness, i.e. type 1, 20 kg; type 2, 40 kg; type 3, 1.0 kg and type 4, 0.5 kg. These four types of test foods were chewed randomly in a fluoroscopic room. The jaw separation distance and the bolus position during first bite and crushing bite were observed. The influence of the chewing order of four types of test foods on the bolus position was also recorded. It was found that both hard and soft test foods were most often crushed at the first molar area, and the separation distance during the crushing bite was only slightly wider than the diameter of the food. The first bite jaw separation distance for hard food chewing was significantly wider than soft food chewing and the later in the chewing order the wider the separation distance. The effect of chewing order was not significant on the position and jaw separation distance of the crushing bite.

Exon 8 mutation of p53 gene associated with nodal metastasis in non-small-cell lung cancer

The epidemiologic characteristics of lung cancer in Taiwan differ from those in other parts of the world in low male-to-female ratio, the high percentage of adenocarcinoma, and the relatively high percentage of nonsmokers who are victims. To investigate possible correlation between p53 gene alteration and the unique characteristics of lung cancer here, p53 gene status of 36 patients with primary, resected non-small-cell lung cancer (NSCLC) was studied by directly sequencing the cDNA of the p53 gene, then acquiring clinical and pathologic data to correlate p53 gene status with clinical parameters and pathologic staging. Missense mutations were present in 42% (15 of 36) of patients with NSCLC, including 42% (10 of 24) with adenocarcinomas, and 45% (five of 11) with squamous cell carcinomas. The frequency of p53 mutation was 50% in smokers and 29% in nonsmokers (p = 0.355). The mutation occurred most frequently in exon 8 (56%), and G:C to A:T transitions in non-CpG or CpG sites were the most commonly observed base changes (56%). These findings differ from the high prevalence of G to T transversion found in previous reports. The frequency of metastasis in hilar and mediastinal lymph nodes was significantly higher in tumors with p53 mutations. The association with nodal stage was strong for mutations within exon 8, but it was less apparent for mutations in other exons probably because of the small number. This study suggests that p53 gene missense is common in NSCLC in Taiwan, but smoking is probably not the sole contributing factor. More interestingly, p53 gene mutations, especially those in exon 8, may be associated with regional nodal metastasis.

[Dento-facial structural characteristics in Angle Class II malocclusion associated with abnormal facial divergency]

Lateral cephalometric radiographs of 60 adult patients with Angle class 11 malocclusion associated with abnormal facial divergency were collected from the Orthodontic Department of the National Taiwan University Hospital. They were divided into a hyperdivergent group (35 cases) and a hypodivergent group (25 case), according to mandibular plane angle (SN-MP). The 19 landmarks on each cephalometric tracing were digitized into a computer, then computer-aided cephalometric analysis was performed to calculate the 17 skeletal measurements and 13 dentoalveolar measurements. The dento-facial structural characteristics of the hyperdivergent and hypodivergent groups were compared. It was found that the subjects of the hyperdivergent group revealed a greater tendency of divergency in the anterior cranial base plane, Frank-fort horizontal plane, palatal plane, occlusal plane, and mandibular plane. Hyperdivergent facial type, supposedly indicating an open bite or a tendency toward an open bite, has a longer lower anterior facial height, shorter posterior facial height, longer upper anterior and posterior dental height. While, the majority of dentofacial characteristics of the hypodivergent facial type observed in is study were directly opposite to those of the hyperdivergent facial type. The relationships of incisor overbite depth and other skeletal and dentoalveolar parameters were illustrated by Pearson's correlation coefficient and stepwise multiple regression analysis by means of the SPSS/PC statistic program. With the incisor overbite depth as the dependent variable, the independent variables included on the regression analysis were the 10 items of skeletal and dentoalveolar parameters. The compared parameters showed a statistically significant correlation with the incisor overbite depth (P < 0.001). By the stepwise method, the variables included on the regression equation were (1) N-Go-Gn, (2) A-Gn-Ar, (3) N-Ans/ans-Me, and (4) U1L1. The value of R square (R2) in the regression analysis was 0.543. It demonstrated that only a 54.3% variation in incisor overbite depth can be explained by variations in those skeletal and dentoalveolar variables.

[The vector analysis of the anteroposterior relationship among the apical bases and the incisors]

Using the lateral cephalometric radiographs, the points A, B, maxillary incisor tip (U) and mandibular incisor tip (L) were projected onto the Frankfort horizontal plane and the projected points were defined as a, b, u and 1, respectively. According to the principle of the vector analysis, the vector formula ab - ul = au - bl can always stand irrespective of how the locations of the points a, b, u and 1 vary. The vectors ab, ul, au and bl represent the anteroposterior linear relationship between the upper jaw and the lower jaw, the upper incisor and the lower incisor (overjet), the upper jaw and the upper incisor, and the lower jaw and the lower incisor, respectively with reference to the FH plane. The lateral cephalometric radiographs taken from a total of 863 class I subjects, including 422 males and 441 females, were submitted for the study. The four vector values were obtained from the tracing of each radiograph and the mean values were computed according to sex and age. If a positive value was given to the vector ab, it denoted that point "a" was anterior to point "b", while a negative value denoted that "a" was posterior to "b". Both sexes of the subjects were divided according to their ages into junior primary (JP, 6-8 years), senior primary (SP, 9-11 years), junior high (JH, 12-14 years), and senior high (SH, 15-18 years) groups. No substantial or significant mean difference of each vector between the males and the females in each age group was noted. The mean values of the vector ab were 7.4, 6.8, 6.1 and 4.7 mm in JP, SP, JH and SH groups, respectively with the male and the female data pooled together. This indicates that there was a gradual catching up tendency of mandibular versus maxillary growth. The mean values of the vector ul were 1.4, 2.8, 2.9 and 2.8 mm in each successive age group, respectively showing that the overjet was rather constant with age except in the youngest group. The corresponding mean values were -0.4, -3.9, -5.2 and -6.1 mm for the vector au and -6.3, -8.0, -8.4 and -8.0 mm for the vector bl in JP, SP, JH and SH groups, respectively. The data indicate that both upper and lower incisors were relatively more upright in the youngest group when compared with the other age groups. In the remaining groups the upper incisors exhibited a tendency of gradual labial tipping with age, whereas the lower incisors kept stable in the procumbency.(ABSTRACT TRUNCATED AT 400 WORDS)

The influence of dental occlusion on electromyographic silent periods

Electromyographic silent periods (EMG SP) and occlusal contact intensity were studied in 31 young patients (9-18 years of age) having different types of malocclusion. EMG SP was induced from bilateral temporalis and masseter muscles by chin tapping during isometric contraction. The simple silent period (SSP), depressed activity (DP) and double silent period (2SP or 3SP) were classified according to the character of silence. The occlusal contact intensity was obtained by using a polymer wafer for clenching and was analysed with a photocclusion analyser. It was found that the average amplitude of temporalis and masseter muscles during clenching was about 400 microV. The mean SSP was around 34 msec. The total SP was around 40 msec in temporalis and 44 msec in masseter. All of the subjects demonstrated one or more DP in ten taps while 18 of them had 2SP or 3SP. The difference in contact intensity between right and left had a strong correlation with the EMG SSP+DP, SSP+2SP3SP and total SP. Anterior-posterior difference was not as strongly related to SP parameters. Less significant correlation was found between SSP and occlusal intensity. It is concluded that the influence of occlusion on EMG SP is basically related to the uneven occlusal contact between the two sides rather than the total occlusal contact intensity or the difference in intensity anterior-posteriorly.

Effects of instantaneous prestretching on force degradation characteristics of orthodontic plastic modules

The object of this study was to investigate the effect of instantaneous prestretching on the force degradation behavior of three kinds of four-link plastic modules. A simple sliding apparatus was used to prestretch instantaneously the plastic modules to 100, 200 and 300% of their original length. After prestretching, specimens were tested at 20, 25 and 30 mm stretch distances. Force measurements were performed at the following occasions: before prestretching; at the end of prestretching; after 1, 4 and 24 hours; and after 1, 2 and 3 weeks. The following conclusions can be drawn from this investigation: The control specimens which had not been instantaneously prestretched exhibited considerable force loss over the three-week test period. Most of the force loss occurred rapidly during the first few hours, with a much lower subsequent force degradation rate. Instantaneous prestretching to a greater length resulted in a lower force value remaining at the end of prestretching. Instantaneous prestretching of the plastic modules is an efficient method to dissipate the high initial force level which is clinically undesirable. Prestretching of the modules around or slightly longer than the stretch distance could reduce the high initial force level and still maintain the same force level as the control groups. However, if the length of instantaneous prestretching of the four-link plastic module was much longer than the testing stretch distance which corresponds to the average distance from the first molar to the canine in the same quadrant, the prestretching would reduce both the high initial force value and the force value during the three-week test period, as compared with the control group.

The relationship of dental crowding to tooth size, dental arch width, and arch depth

This study was undertaken to answer the question, "Are there any differences in the mesiodistal tooth diameters, dental arch width and dental arch depth between the crowded and noncrowded dentitions?" The materials submitted for study consisted of the Orthoscan intraoral occlusograms of 89 subjects with well-aligned dentition and those of 74 subjects with gross dental crowding. The tooth size and arch dimensions were measured from these intraoral occlusograms. The data were subjected to statistical treatment for comparison of noncrowded and crowded groups. The findings in this study lead to the following conclusions: The mesiodistal tooth diameters of the crowded group were significantly larger than those of the noncrowded group. The dental arch widths of the crowded group were significantly smaller than those of the noncrowded group. No substantial or significant difference in dental arch depth between the crowded and noncrowded subjects could be noted. From these findings it seems that tooth size and dental arch width are determining factors in the formation of dental crowding. Clinically, these results suggest that in the treatment of dental crowding, extraction of teeth and/or expansion of dental arches should be considered depending on what is the main causative factor.

Acute and chronic effects of haloperidol on plasma and brain homovanillic acid in the rat

The effects of acute and chronic administration of haloperidol on homovanillic acid (HVA) in plasma and the brain were examined in the rat. Acute haloperidol treatment (1 mg/kg) resulted in highly significant elevations in HVA within 30 min and produced a maximal increase of HVA in 3-6 hr in both plasma and the whole brain. The response of brain HVA to increasing doses (0.05-30 mg/kg) of haloperidol showed an inverted U pattern. Plasma HVA showed a very flat response to lower doses (less than or equal to 5 mg/kg) of haloperidol and a dramatically elevated one to higher doses (greater than or equal to 10 mg/kg). Haloperidol produced a parallel increase in plasma and brain HVA at lower doses (less than or equal to 2 mg/kg) only. After chronic administration of haloperidol for up to 28 days, the response of HVA in plasma correlated mainly with, but tolerated later than, those in the whole brain and the olfactory tubercle.