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Recently a dark matter-electron (DM-electron) paradigm has drawn much attention. Models beyond the standard halo model describing DM accelerated by high energy celestial bodies are under intense examination as well. In this Letter, a velocity components analysis (VCA) method dedicated to swift analysis of accelerated DM-electron interactions via semiconductor detectors is proposed and the first HPGe detector-based accelerated DM-electron analysis is realized. Utilizing the method, the first germanium based constraint on sub-GeV solar reflected DM-electron interaction is presented with the 205.4 kg·day dataset from the CDEX-10 experiment. In the heavy mediator scenario, our result excels in the mass range of 5-15 keV/c^{2}, achieving a 3 orders of magnitude improvement comparing with previous semiconductor experiments. In the light mediator scenario, the strongest laboratory constraint for DM lighter than 0.1 MeV/c^{2} is presented. The result proves the feasibility and demonstrates the vast potential of the VCA technique in future accelerated DM-electron analyses with semiconductor detectors.
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This study used machine learning techniques combined with routine blood cell analysis parameters to build preliminary prediction models, helping differentiate patients with depression from healthy controls, or patients with anxiety. A multicenter study was performed by collecting blood cell analysis data of Beijing Chaoyang Hospital and the First Hospital of Hebei Medical University from 2020 to 2021. Machine learning techniques, including support vector machine, decision tree, naïve Bayes, random forest and multi-layer perceptron were explored to establish a prediction model of depression. The results showed that based on the blood cell analysis results of healthy controls and depression group, the accuracy of prediction model reached as high as 0.99, F1 was 0.975. Receiver operating characteristic curve area and average accuracy were 0.985 and 0.967, respectively. Platelet parameters contributed mostly to depression prediction model. While, to random forest differential diagnosis model based on the data from depression and anxiety groups, prediction accuracy reached 0.68 and AUC 0.622. Age, platelet parameters, and average volume of red blood cells contributed the most to the model. In conclusion, the study researched on the prediction model of depression by exploring blood cell analysis parameters, revealing that machine learning models were more objective in the evaluation of mental illness.
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Depressão , Aprendizado de Máquina , Humanos , Teorema de Bayes , Máquina de Vetores de Suporte , Contagem de Células SanguíneasRESUMO
Objective: To analyze the pathological classification of malignant peritoneal mesothelioma (MPeM) and screen the immunohistochemical markers that can distinguish MPeM from peritoneal metastatic carcinoma (PC) . Methods: In June 2020, the pathological results of peritoneal biopsy of 158 MPeM and 138 PC patients from Cangzhou Central Hospital, Cangzhou People's Hospital, and Cangzhou Hospital of Integrated Traditional Chinese and Western Medicine from May 2011 to July 2019 were retrospectively analyzed, and the pathological classifications of MPeM in Cangzhou were summarized. Immunohistochemical markers of MPeM and PC patients were analyzed, and receiver operating characteristic curve (ROC curve) was drawn for differential diagnosis of MPeM and PC. Results: There were 55 male and 103 female MPeM patients in Cangzhou, with an average age of 57.1 years old. The asbestos exposure rate was 91.14% (144/158). The most common pathological classifications were cutaneous type, accounting for 90.51% (143/158). There were significant differences in the expression of calreticulum protein, CK5/6, vimentin, D2-40, carcinoembryonic antigen (CEA) and tail type homologous nuclear gene transcription factor 2 (CDX-2) between MPeM and PC (P<0.05). Among the 6 positive markers, the sensitivity of calreticulum protein was the highest (0.905) and CEA was the lowest (0.428) . Conclusion: Calreticulum protein, CK5/6, vimentin, D2-40, CEA and CDX-2 may be used as specific markers to distinguish the diagnosis of MPeM from PC.
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We present improved germanium-based constraints on sub-GeV dark matter via dark matter-electron (χ-e) scattering using the 205.4 kg·day dataset from the CDEX-10 experiment. Using a novel calculation technique, we attain predicted χ-e scattering spectra observable in high-purity germanium detectors. In the heavy mediator scenario, our results achieve 3 orders of magnitude of improvement for m_{χ} larger than 80 MeV/c^{2} compared to previous germanium-based χ-e results. We also present the most stringent χ-e cross-section limit to date among experiments using solid-state detectors for m_{χ} larger than 90 MeV/c^{2} with heavy mediators and m_{χ} larger than 100 MeV/c^{2} with electric dipole coupling. The result proves the feasibility and demonstrates the vast potential of a new χ-e detection method with high-purity germanium detectors in ultralow radioactive background.
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Eletricidade , ElétronsRESUMO
A search for exotic dark matter (DM) in the sub-GeV mass range has been conducted using 205 kg day data taken from a p-type point contact germanium detector of the CDEX-10 experiment at China's Jinping underground laboratory. New low-mass dark matter searching channels, neutral current fermionic DM absorption (χ+Aâν+A) and DM-nucleus 3â2 scattering (χ+χ+AâÏ+A), have been analyzed with an energy threshold of 160 eVee. No significant signal was found; thus new limits on the DM-nucleon interaction cross section are set for both models at the sub-GeV DM mass region. A cross section limit for the fermionic DM absorption is set to be 2.5×10^{-46} cm^{2} (90% C.L.) at DM mass of 10 MeV/c^{2}. For the DM-nucleus 3â2 scattering scenario, limits are extended to DM mass of 5 and 14 MeV/c^{2} for the massless dark photon and bound DM final state, respectively.
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Núcleo Celular , FótonsRESUMO
Among the staff of Beijing Chao-Yang Hospital, Capital Medical University, who received the inactivated SARS-CoV-2 vaccine on January 30 in 2021, 28 recipients were selected for this research. Samples for nucleic acid tests were collected from the surface of the recipients' both hands before and after vaccination. The hemostatic stickers used after the inoculation were also collected for nucleic acid tests. The nucleic acid tests of the samples collected from the surface of both hands of the 28 recipients before vaccination were all negative. After vaccination, the nucleic acid tests of the samples collected from the surface of both hands of recipients were positive in 3 cases, and suspicious in 8 cases, with a positive rate of 10.7%. A total of 25 hemostatic stickers used were collected, 24 of them had positive nucleic acid tests, and the rest one had suspicious nucleic acid test result, with a positive rate of 96%. The hemostatic stickers used after the inoculation have the risk of nucleic acid contamination.
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COVID-19 , Hemostáticos , Ácidos Nucleicos , Vacinas contra COVID-19 , Humanos , SARS-CoV-2 , VacinaçãoRESUMO
Objective: To explore the association between serum brain-derived neurotrophic factor and clinical stage and dysmenorrhoea of endometriosis. Methods: A total of 82 patients were studied with laparoscopically diagnosed endometriosis between June 2017 and June 2019, and 75 healthy women with reproductive age were selected as the control group during the same period. The endometriosis patients were scored by visual analogue scale(VAS)according to their preoperative dysmenorrhoea.And endometriosis was staged and scored according to the score of Revised American Fertility Society(r-AFS).Enzyme-linked immunosorbent assay (ELISA) was used to determine preoperative BDNF level in serum, and the correlation between BDNF level with clinical stage as well as dysmenorrhea of endometriosis were analysed. Results: The serum BDNF level in endometriosis patients was (1 082±43) ng/L, significantly higher than that in the normal control [(649±30) ng/L], there was statistical difference between the two groups(P<0.001). The BDNF expression in patients with r-AFS stage â ¢-â £ was higher than that in patients with â -â ¡ stage [(1 164±389) ng/L vs (791±218)ng/L, P<0.001]. BDNF level in serum was closely correlated with the degree of dysmenorrhea (r=0.682), and the BDNF level in patients with moderate or severe dysmenorrhea was significantly higher than that in patients without dysmenorrhea and patients with mild dysmenorrhea [(1 292±43) ng/L vs(718±36) ng/L, P<0.001]. Conclusions: The serum BDNF level in endometriosis patients is positively correlated with clinical stage and dysmenorrhea.
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Dismenorreia , Endometriose , Fator Neurotrófico Derivado do Encéfalo , Feminino , HumanosRESUMO
Objective: To explore the relationship between the new Tumor-Node-Metastasis (TNM) staging system and the serum CA125 level with the prognosis of malignant peritoneal mesothelioma (MPeM) . Methods: The clinical data of 74 patients with MPeM diagnosed by pathology and immunohistochemistry were collected from January 2005 to June 2016 in Cangzhou Central Hospital. According to the results of CT-peritoneal carcinoma index (PCI) , the tumor load was divided into T1 (PCI 1-10) , T2 (PCI 11-20) , T3 (PCI 21-30) and T4 (PCI 31-39) , combined with lymph node metastasis and extraperitoneal metastasis, a new TNM staging system was established. And serum CA125 level was measured in the same time. The median survival time of patients with MPeM, the effect of the new TNM staging system, and serum CA125 levels on their prognosis were retrospectively analyzed. Results: Among the 74 patients with MPeM, 25 (33.8%) cases were males and 49 (66.2%) cases were females. There were 8 cases with systemic chemotherapy, 8 cases with heated intraperitoneal chemotherapy, and 1 case with combination chemotherapy. 10 cases were T1, 22 cases were T2, 27 cases were T3, 15 cases were T4, 12 cases had lymph node metastasis and 10 cases had distant metastasis. The median survival time of T1, T2, T3 and T4 were 12, 10, 6 and 3 months respectively. There were 38 (77.6%) cases with high serum CA125 in all 49 cases who have been tested for CA125. The median survival time of positive group and negative group were 6 months and 11 months respectively. 68 (91.9%) patients had died by the end of collecting data. The median survival time was 8 months. Univariate analysis showed that there were significant differences in survival time between patients with different CT-PCI stages, serum CA125 levels, and with or without lymph node and extraperitoneal metastasis (P<0.05) . Multivariate analysis showed that CT-PCI was independent risk factors for the prognosis of MPeM (HR=2.203, 95%CI: 1.475-3.289) . Conclusion: The new TNM staging system and serum CA125 are important for the prognosis of patients with MPeM. Early detection, early diagnosis and comprehensive treatment can improve the survival time of patients with MPeM.
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Mesotelioma , Neoplasias Peritoneais , Antígeno Ca-125/análise , Feminino , Humanos , Masculino , Proteínas de Membrana/análise , Mesotelioma/diagnóstico , Estadiamento de Neoplasias , Neoplasias Peritoneais/diagnóstico , Prognóstico , Estudos Retrospectivos , Taxa de SobrevidaRESUMO
A critical challenge facing the basic long-pulse high-confinement operation scenario (H mode) for ITER is to control a magnetohydrodynamic (MHD) instability, known as the edge localized mode (ELM), which leads to cyclical high peak heat and particle fluxes at the plasma facing components. A breakthrough is made in the Experimental Advanced Superconducting Tokamak in achieving a new steady-state H mode without the presence of ELMs for a duration exceeding hundreds of energy confinement times, by using a novel technique of continuous real-time injection of a lithium (Li) aerosol into the edge plasma. The steady-state ELM-free H mode is accompanied by a strong edge coherent MHD mode (ECM) at a frequency of 35-40 kHz with a poloidal wavelength of 10.2 cm in the ion diamagnetic drift direction, providing continuous heat and particle exhaust, thus preventing the transient heat deposition on plasma facing components and impurity accumulation in the confined plasma. It is truly remarkable that Li injection appears to promote the growth of the ECM, owing to the increase in Li concentration and hence collisionality at the edge, as predicted by GYRO simulations. This new steady-state ELM-free H-mode regime, enabled by real-time Li injection, may open a new avenue for next-step fusion development.
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An electrostatic coherent mode near the electron diamagnetic frequency (20-90 kHz) is observed in the steep-gradient pedestal region of long pulse H-mode plasmas in the Experimental Advanced Superconducting Tokamak, using a newly developed dual gas-puff-imaging system and diamond-coated reciprocating probes. The mode propagates in the electron diamagnetic direction in the plasma frame with poloidal wavelength of â¼8 cm. The mode drives a significant outflow of particles and heat as measured directly with the probes, thus greatly facilitating long pulse H-mode sustainment. This mode shows the nature of dissipative trapped electron mode, as evidenced by gyrokinetic turbulence simulations.
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Objective:To explore the equivalence of the test results of the water or air caloric tests and the compliance of the test in the healthy individuals. To provide scientific basis for clinical standardization of caloric test.Method: Randomized crossover clinical trial, 60 healthy individuals were divided into group A and group B. Water caloric test was carried out first in group A, and air caloric test was carried out after elution effect(one day interval). The treatment of group B was opposite to group A. SPV(Slow Phase Velocity), CP(canal paralysis) and SPV and CP' s 95%CI were used as evaluation indexes to analyze the equivalence of water and air caloric test in healthy people and the clinical normal reference value and stability and compliance of the water and air caloric test. Result: â 60 cases of caloric test CP value of chi square test suggested that there was no statistical difference between two kinds of media in the examination of the vestibular function of healthy individuals, and the CP value of the two was 85%(51/60). â¡the SPV value of the was obviously higher than that of the air caloric test. The SPV value at each temperature of the water caloric test stimulation is quite different from the air caloric test stimulation. â¢The range of water caloric test stimulation CP 95%CI was 8%-12%, and the average value was 10%. The interval of air caloric test stimulation CP 95%CI was 10%-15% and the average value was 12%. â£This study provided the corresponding SPV 95%CI as the medical reference values. â¤The subjects of 98.33%(59/60) of the questionnaire survey selecting air caloric test and the results of the observation indicated that the duration of the air caloric test was shorter and more comfortable. Conclusion: â Air caloric test can satisfied the needs of clinical assessment of horizontal semicircular canal function, and can make patients feel more comfortable. However, due to the weak intensity of nystagmus, water caloric test has to be used when the SPV value is too low. â¡In this study, the upper limit of the CP value of the air caloric test in healthy individuals was 0.21, which is quite different from the upper limit of the standard value was 0.25 of the water caloric test. Therefore, the laboratory should establish their own reference value of the laboratory caloric test, and should not blindly apply the standard value of the water caloric test as the standard of the hemiplegia of the unilateral semicircular canal. The results of this study suggest that air caloric test can be used instead of water caloric test in clinic. And if the patient has no contraindications, air caloric test can be used as a priority.
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OBJECTIVE: The present study is aimed to explore the correlation between PAI-1 gene mediated by NF-κB signaling pathway and human sepsis. PATIENTS AND METHODS: In this study, we used 74 cases of sepsis patients preserved by the laboratory as the observation group, and 68 cases of healthy people served the control group. Further methods like fluorescence quantitative PCR, enzyme-linked immunosorbent assay, Western-blotting were used to determine NF-B expression, NF-κB gene mRNA analyses and protein expression on different research subjects. Further, the positive expression rates of PAI-1 gene in the observation group and the control group were determined by immunohistochemistry. RESULTS: The expression levels of NF-κB and PAI-1 gene mRNA in the blood of the observation group significantly increased in comparison to control group (X2 = 3.24, p < 0.05; X2 = 2.81, p < 0.05). Also, NF-κF and PAI-1 gene protein expressions (0.14 ug/l, 0.32 ug/l) were significantly higher in the observation group in comparison to control group (p < 0.05). The results of blood glucose measurement showed that the fasting blood glucose (14.3 mmol/l) in the observation group was significantly higher than that in the control group (4.6 mmol/l). Immunohistochemical were also in sync with above results. CONCLUSIONS: The present study concludes that PAI-1 gene expression gets significantly increased via NF-κF signaling pathway during sepsis.
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NF-kappa B/metabolismo , Inibidor 1 de Ativador de Plasminogênio/genética , Sepse/genética , Transdução de Sinais , Adolescente , Adulto , Glicemia/análise , Estudos de Casos e Controles , Expressão Gênica , Humanos , Pessoa de Meia-Idade , Adulto JovemRESUMO
Cholera toxin (CT) stimulated adenylate cyclase and a phospholipase which elevated cellular levels of 3',5'-cyclic adenosine monophosphate (cAMP) and arachidonic acid (AA). The AA was quickly converted to prostaglandins (PGs) via the cyclo-oxygenase pathway. Chloroquine exerted minimal inhibition of cAMP levels in CT-treated cells, although CT-induced release of [3H]AA and PGs was blocked completely when the drug was added in concentrations as low as 0.1 mM (50 micrograms/ml). Inhibition of [3H]AA release was complete when chloroquine was added before or within 30 min after CT. The capacity of chloroquine to inhibit either phospholipase C (PLC) or phospholipase A2 (PLA2) could explain the antisecretory activity of this drug.
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Ácidos Araquidônicos/metabolismo , Cloroquina/farmacologia , Toxina da Cólera/antagonistas & inibidores , Prostaglandinas/metabolismo , Animais , Ácido Araquidônico , Linhagem Celular , AMP Cíclico/metabolismo , Técnicas In Vitro , Macrófagos , Camundongos , Fatores de TempoRESUMO
Primary A-delta nociceptive neurons in the trigeminal ganglia of immobilized crotaline snakes were examined by intrasomal recording and injection of horseradish peroxidase in vivo. Thirty-four neurons supplying the oral mucosa or facial skin were identified as A-delta nociceptive neurons which responded exclusively to noxious mechanical stimuli and had a peripheral conduction velocity ranging from 2.6 to 15.4 m/s. These neurons were subdivided into a fast-conducting type (FC-type) and a slowly conducting type (SC-type). Neurons of both types had a receptive field limited to a single spot which responded to pin prick stimulus with a threshold of more than 5 g. The FC-type neurons had a narrow spike followed by a shorter after-hyperpolarization. In contrast, SC-type neurons exhibited a broad spike with a hump on the falling phase and a longer after-hyperpolarization. The diameters of the stem, central and peripheral axons of the FC-type neurons were significantly thicker than those of the SC-type neurons, but there was no statistical difference in the soma size of the two types. Central axons of both types of neurons were thinner than their stem and peripheral axons. Dichotomizing fibers of peripheral axons were observed within the ganglion on 3 neurons. Central axons of the FC-type neurons terminated ipsilaterally in the nucleus principalis, the subnucleus oralis, interpolaris and caudalis and the interstitial nucleus, whereas those of the SC-type neurons generally projected only to the caudal half of the subnucleus interpolaris, subnucleus caudalis and interstitial nucleus ipsilaterally. The present data showed for the first time the physiological and morphological heterogeneity of the primary trigeminal A-delta nociceptive neurons and revealed that the trigeminal nucleus principalis and all the subdivisions of the trigeminal descending nucleus are involved in nociception as relay nuclei, but the subnucleus caudalis and the caudal half subnucleus interpolaris are the essential relay sites of the primary nociceptive afferents supplying the oral mucosa and facial skin. The interstitial nucleus also appears to play an important role in orofacial nociception.
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Axônios/fisiologia , Mucosa Bucal/inervação , Neurônios/fisiologia , Dor/fisiopatologia , Pele/inervação , Serpentes/fisiologia , Potenciais de Ação/fisiologia , Animais , Fenômenos Biomecânicos , Estimulação Elétrica , Feminino , Masculino , Vias Neurais/fisiologia , Neurônios/ultraestrutura , Nervos Periféricos/ultraestrutura , Serpentes/anatomia & histologia , Gânglio Trigeminal/ultraestruturaRESUMO
Intrasomal recording and horseradish peroxidase injection techniques were employed in vivo to determine the morphological characteristics of touch, temperature, and mechanical nociceptive neurons in the trigeminal ganglia of crotaline snakes. The touch neurons, with a peripheral axon conducting at the A-beta range, could be subdivided into tactile and vibrotactile neurons according to their response properties, but there were no morphological differences between them. These neurons exhibited a large and oval soma and possessed a set of large stem, peripheral, and central axons which were all myelinated and equal in diameter with a constriction at the bifurcation. The temperature neurons, which conducted peripherally at the A-delta range, were physiologically separated into thermosensitive and thermo-mechanosensitive neurons, which were also morphologically indistinguishable. The temperature neurons had a round soma of medium size and a set of medium axons with varied axonal bifurcation patterns. All axons of these neurons were myelinated, but the central axon was thinner than the stem and peripheral axons. The mechanical nociceptive neurons, which had a peripheral axon conducting at the A-delta range, were morphologically heterogeneous based on their conduction velocities. The neurons conducting at the fast A-delta range were morphologically similar to the temperature neurons in the ganglion excepting their thinner central axons, whereas those at the slow A-delta range had a thinner myelinated stem axon that gave rise to a thinner myelinated peripheral axon and an unmyelinated stem axon with a bifurcation of either a triangular expansion at the bifurcating point or a central axon arising straightforwardly from the constant stem and peripheral axons. This study revealed that distinct morphological characteristics do exist for the touch and temperature neurons and the subtypes of mechanical nociceptive neurons in the trigeminal ganglion, but not for the subfunctional types of touch neurons or temperature neurons.
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Neurônios/classificação , Neurônios/fisiologia , Nociceptores/fisiologia , Temperatura , Tato/fisiologia , Gânglio Trigeminal/fisiologia , Animais , Axônios/fisiologia , Contagem de Células , Feminino , Peroxidase do Rábano Silvestre , Masculino , SerpentesRESUMO
Cholera toxin (CT) stimulated phospholipase activity and caused [3H]arachidonic acid (3H-AA) release in a murine macrophage/monocyte cell line. Pretreatment of cells with dexamethasone, a phospholipase A2 (PLA2) inhibitor, did not affect CT-induced 3H-AA release. In contrast, aspirin, which is an inhibitor of phospholipase C (PLC), blocked CT-induced 3H-AA release and subsequent prostaglandin (PC) synthesis. The inhibitory effect of aspirin was dose dependent, with 4 mM reducing the CT response by approximately 50%. Similarly, inhibition was time dependent, occurring when the drug was added to the culture medium as late as 30 min after CT. Brief exposure (30 min) of the cells to aspirin did not alter their subsequent response to CT, but 3H-AA release from cells exposed to aspirin for 2.5 h was irreversibly inhibited. The data suggested that CT stimulation of AA metabolism may involve increased PLC activity.
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Aspirina/farmacologia , Toxina da Cólera/farmacologia , Macrófagos/enzimologia , Fosfolipases/metabolismo , Prostaglandina-Endoperóxido Sintases/metabolismo , Animais , Ácidos Araquidônicos/metabolismo , Células Cultivadas , Cromatografia Líquida de Alta Pressão , Dexametasona/farmacologia , Relação Dose-Resposta a Droga , Macrófagos/efeitos dos fármacos , Camundongos , Fosfolipases A/metabolismo , Fosfolipases A2 , Prostaglandinas/biossíntese , Fatores de Tempo , Fosfolipases Tipo C/metabolismoRESUMO
Using 32 Crotaline snakes, Trimeresurus flavoviridis, intrasomal recordings were made from 44 neurons of the trigeminal ganglia in vivo. They were 10 C neurons from 9 snakes and 34 A-delta mechanical nociceptive neurons from 23 snakes. 5 of the 10 C neurons were identified as mechanical nociceptive neurons. The neurons were labeled with iontophoretically injected HRP. Each of the 5 C nociceptive neurons had one receptive field, on which 1 spike was elicited by pricking the skin or mucosa with a pin. They were sensitized after repeated stimulation. The fields were insensitive to thermal stimulation. No background discharge was observed. Average conduction velocity was 0.95 m/s (+/- 0.4 S.D., n = 5). Mean resting potential was -62.5 mV (+/- 6.0 S.D., n = 4), and mean action potential amplitude was 88.0 mV (+/- 10.9 S.D., n = 4). Two somata were successfully visualized with HRP (22 microns x 20 microns, 20 microns x 18 microns). Total lengths of labeled axons were 1260 and 1480 microns peripherally to the edge of the section, and 1810 and 770 microns centrally. Neither of the neurons had branching of the peripheral or central axons in the ganglion.
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Mecanorreceptores/fisiologia , Fibras Nervosas/fisiologia , Nociceptores/fisiologia , Gânglio Trigeminal/fisiologia , Trimeresurus/fisiologia , Potenciais de Ação/fisiologia , Animais , Axônios/fisiologia , Histocitoquímica , Peroxidase do Rábano Silvestre , Gânglio Trigeminal/citologiaRESUMO
Medullary thyroid carcinoma (MTC) is a cancer that is relatively insensitive to clinical chemotherapy. Our previous studies have demonstrated that an established human MTC cell line, TT, seems to possess an intrinsic resistance phenotype when tested for its chemosensitivity to multiple antineoplastic agents. We now report our investigation on the potential mechanisms responsible for the chemoresistance of TT cells. Northern analysis showed an increased level of multidrug resistance gene (mdrl) mRNA in TT and in an inherently drug-resistant colon carcinoma cell line, LoVo, when compared with CEM, a drug-sensitive leukemic lymphoblastic cell line; the latter two cell lines were included here as a control. Verapamil (10 microM) partially reversed resistance to doxorubicin in TT and LoVo cells, but had no effect on doxorubicin cytotoxicity to CEM cells. Expression of glutathione-S-transferase-pi (GST pi) gene was undetectable in TT, whereas, under similar conditions, GST pi mRNA was detectable in LoVo. Growth kinetics studies revealed that doubling times of the 3 cell lines in exponential growth were 95, 37, and 24 h for TT, LoVo and CEM, respectively. Flow-cytometric analysis showed that the percentage of TT population is S phase was 49% and 33% of the LoVo and CEM cell populations, respectively, while the G1/G0 fraction of TT was about 63% and 61% higher than that of LoVo and CEM, respectively. Our data suggest that the intrinsic chemoresistance in TT cells may be attributed to the combined factors of overexpression of the mdrl gene, a slower growth rate and a smaller proliferation fraction, although other factors or mechanisms that are yet to be investigated may also act in concert to contribute to the resistance phenotype of TT.