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1.
Article Zh | MEDLINE | ID: mdl-38311956

The risk management in workplace is an important measure to effectively prevent and control the harm of hand-transmitted vibration. Based on the relevant developments at home and abroad, this paper expounds the risk of manual vibration operation in workplace by taking contact assessment and hazard assessment as an example. On this basis, the limit management and hierarchical management related to risk management are discussed, and the existing problems are analyzed.


Occupational Exposure , Vibration , Vibration/adverse effects , Hand , Workplace , Risk Management
3.
Zhonghua Yi Xue Za Zhi ; 100(44): 3529-3533, 2020 Dec 01.
Article Zh | MEDLINE | ID: mdl-33256297

Objective: To investigate the effect of bone marrow mononuclear cell transplantation on the expression of miRNA-21 and miRNA-155 in mice with ulcerative colitis(UC). Methods: Healthy and clean KM mice aged 6-8 weeks were randomly divided into transplantation group, model group and normal control group with 15 mice in each group. In the transplantation group and model group, dextran sodium sulfate (DSS) was used to establish the model for 24 h. The mice in the transplantation group were injected with 0.4 ml of 4 ', 6-diaminol-2-phenylindole (DAPI) -labeled P3-BM-MNCs cell suspension (3.2×10(6) cells/ml), and the mice in the model group and the normal control group were injected with 0.4 ml phosphate buffer (PBS).UC disease activity index (DAI) was used to test the general condition of mice; HE staining was used to observe the pathological changes of colon tissue; Real-time quantitative PCR was used to detect the expression of miRNA-21 and miRNA-155 mRNA. Results: DAI scores of normal control group, model group and transplantation group were 0 (0,1), 3.1 (2.8,3.3) and 2.7 (2.4,3.1),respectively. Compared with normal control group, the DAI score of model group and transplantation group was higher (P<0.05), and the DAI score of transplantation group was lower than that of model group (P<0.05). The gross scores of tissue injury in normal control group, model group and transplantation group were 0 (0, 1), 3 (3, 4) and 1 (1, 2), respectively,and the pathological scores of tissue injury were 0 (0, 1), 16 (12, 16) and 6 (6, 8), respectively,compared with the normal control group. The tissue injury score of the model group and the transplantation group was higher (P<0.05), and the tissue injury score of the transplantation group was lower than that of the model group (P<0.05). The expression levels of miRNA-21 mRNA in normal control group, model group and transplantation group were 0.87±0.15, 2.38±0.29 and 1.59±0.32, respectively, and the expression levels of miRNA-155 mRNA were 1.87±0.46, 7.38±1.97 and 3.92±0.84, respectively, compared with the normal control group, the expression of miRNA-21 and miRNA-155 mRNA in the model group and transplantation group was higher (P<0.01), the expression of miRNA-21 and miRNA-155 mRNA in the transplantation group was lower than that of the model group (P<0.05). Conclusion: Bone marrow mononuclear cell transplantation can improve the histopathological and DAI scores of mice with UC, which may be related to the down-regulation of miRNA-21 and miRNA-155 mRNA expression.


Colitis, Ulcerative , MicroRNAs , Animals , Bone Marrow , Cell Transplantation , Colon , Dextran Sulfate , Disease Models, Animal , Mice , MicroRNAs/genetics
4.
Zhonghua Yi Xue Za Zhi ; 99(25): 1963-1967, 2019 Jul 02.
Article Zh | MEDLINE | ID: mdl-31269601

Objective: To investigate the cinical value of FAM19A4promoter methylation in cervicalexfoliated cells for triage of cervical cancer. Methods: A total of 162 high-risk HPV-infected patients who were pathologically confirmed as different cervical lesions from August 2017 to December 2017 were collected in Guangdong Women and Children Hospital. Taqman probe-based quantitative PCR (qPCR) was used to detect the methylation of FAM19A4 promoterin different grades of cervical lesions, and the value of FAM19A4 methylation in predicting cervical HSIL and the above lesions was calculated by diagnostic test. Results: (1)The positive rates of FAM19A4 methylation in cervical exfoliated cells increased with the severity of cervical lesions, which were 7.69% (4/52) , 34.62% (9/26) , 55.56% (20/36) , 95.83% (46/48) in normal cervix/cervicitis, cervical LSIL, HSIL, and cervical cancer, respectively(P<0.05).(2)There was no significant difference in the detection rates of FAM19A4 methylation between different age groups, pathological types, clinical stage, tumor size and lymph node metastasis status (P>0.05). (3) The specificity and positive predictive value of FAM19A4 methylation in detecting cervical HSIL alone and ≥HSIL lesions were the optimal, with the AUC of 0.69 and 0.84, respectively. When combined with HPV16/18 genotyping, the sensitivity was significantly improved. Conclusions: The detection of FAM19A4 promoter methylation in cervical exfoliated cells has a high clinical value of discriminating ≥HSIL lesions; and the cotest of methylated FAM19A4 and HPV16/18 genotyping can identify ≥HSIL lesions more sensitively.


Cytokines/genetics , Papillomavirus Infections , Uterine Cervical Dysplasia , Uterine Cervical Neoplasms , DNA Methylation , Female , Human papillomavirus 16 , Human papillomavirus 18 , Humans , Promoter Regions, Genetic
5.
Bioresour Technol ; 268: 278-285, 2018 Nov.
Article En | MEDLINE | ID: mdl-30086454

Alkali and alkaline earth metal (AAEM) species are the main components of the ash of biomass, and which would influence the combustion of biomass and coal during the co-firing process. The aim of this paper is to investigate the effects of potassium (K), sodium (Na), calcium (Ca), and magnesium (Mg) on the combustion characteristics of pine sawdust (PS) and bituminous coal (BC) by a single particle combustion method. The raw, ash-free and impregnated samples were prepared, and their combustion processes were recorded by a high speed camera. Based on the recorded flame images, the effects of K, Na, Ca and Mg on the combustion characteristics (ignition, volatiles combustion, char combustion) of PS and BC were analyzed. The results reveal that the demineralization treatment brings negative effects on the combustion of PS, which reflects in longer ignition delay time, volatiles and char burnout time, and lower combustion temperature, while the effects on the combustion of BC are opposite. The impregnated samples exhibit shorter ignition delay time, volatiles and char burnout time, and higher combustion temperature than the ash-free samples. In the entire combustion process of PS and BC, K exhibits the strongest promotion effect. When the concentration of K increases from 0 to 2 wt%, the ignition delay time of PS and BC decreases about 5.5 ms and 16.4 ms respectively, the volatiles combustion temperature increases about 41 °C and 77 °C respectively, and the char combustion temperature increases about 226 °C and 141 °C respectively.


Coal , Metals, Alkaline Earth , Wood , Alkalies , Incineration , Thermogravimetry
6.
Horm Metab Res ; 48(5): 318-24, 2016 May.
Article En | MEDLINE | ID: mdl-27050251

To systematically review the efficacy of hCG and LHRH on testicular descent in boys with cryptorchidism, comprehensive search was performed to identify randomized controlled trials (RCTs) in PubMed, EMBASE, the Cochrane Library, Wanfang Database, and China National Knowledge Infrastructure (CNKI) up to March 2014. Outcomes included testicular complete descent rate (TCDR) and cure rate of patients. Study quality was evaluated using the Jadad scale. Meta-analysis was performed using Review Manager software. Finally, 13 studies were included. hCG and LHRH increased TCDR comparing with control group. The success rate of hCG and LHRH was 24 and 19%, respectively. Further, hCG and LHRH had significant effect on bilateral cryptorchidism, but not on unilateral cryptorchidism. All side effects were transitory and not severe, but if they have long-term harms were not clear. hCG and LHRH can effectively increase TCDR and there was no significant difference between them. However, the hormones cannot be recommended for everyone because of their low success rates and potential long-term harms. Further studies are needed to determine the efficacy of hormonal treatment for subtypes of cryptorchidism.


Chorionic Gonadotropin/therapeutic use , Cryptorchidism/drug therapy , Gonadotropin-Releasing Hormone/therapeutic use , Randomized Controlled Trials as Topic , Case-Control Studies , Chorionic Gonadotropin/adverse effects , Gonadotropin-Releasing Hormone/adverse effects , Humans , Male , Treatment Outcome
7.
BMC Genomics ; 17: 142, 2016 Feb 27.
Article En | MEDLINE | ID: mdl-26920613

BACKGROUND: Zinc finger proteins (ZFPs) play an important role in regulating plant responses to abiotic stress. However, little is known about the function of LSD1-like-type ZFP in saline-alkaline (SA) stress resistance of rice. In this study, OsLOL5 (GenBank No. AJ620677), containing two LSD1-like-type C2C2 domains, was isolated and analyzed its protection roles in transgenic plants and yeast. OsLOL5 was located in the nucleus as evidenced by the bombardment of onion epidermal cells. RESULTS: OsLOL5 expression significantly increased in rice leaves and roots under 150 mmol L-1 NaCl, 30 mM NaHCO3, and 10 mmol L-1 H2O2 treatment, respectively. Overexpression of OsLOL5 in yeast resulted in SA tolerance at significant level. Transgenic Arabidopsis plants overexpressing OsLOL5 grew well in the presence of both NaCl and NaHCO3 treatments, whereas wild-type plants exhibited chlorosis, stunted growth phenotype, and even death. SA stress caused significant changes in the malondialdehyde (MDA) contents in non-transgenic plants compared with those in transgenic lines. Transgenic rice overexpressing OsLOL5 exhibited stronger resistance than NT under NaHCO3 treatment, as demonstrated by its greater shoot length, and fresh weight. The genes associated with oxidative stress, such as OsAPX2, OsCAT, OsCu/Zn-SOD, and OsRGRC2, were significantly upregulated in OsLOL5-overexpressing rice. The results suggested that OsLOL5 improved SA tolerance in plants, and regulated oxidative and salinity stress retardation via the active oxygen detoxification pathway. CONCLUSIONS: The yeast INVScI bacterium grew significantly better than the control strain under NaCl, NaHCO3, and H2O2 treatments. These findings illustrated that OsLOL5 overexpression enhanced yeast resistance for SA stress through active oxygen species. The present study showed that the OsLOL5 genes involved in the ROS signaling pathways may combine with the model plant Arabidopsis and rice in LDS1-type ZFP by ROS signaling pathways that regulate cell necrosis. We speculated that the OsLOL5 active oxygen scavenging system may have coordinating roles. The present study further revealed that OsLOL5 ZFP could regulate oxidative stress function, but could also provide a basis for salt-resistant rice strains.


Arabidopsis/physiology , Oryza/genetics , Plant Proteins/genetics , Saccharomyces cerevisiae/physiology , Salt Tolerance/genetics , Arabidopsis/genetics , Cloning, Molecular , Malondialdehyde/metabolism , Oryza/physiology , Oxidative Stress , Plants, Genetically Modified/genetics , Plants, Genetically Modified/physiology , Reactive Oxygen Species/metabolism , Saccharomyces cerevisiae/genetics , Signal Transduction , Stress, Physiological , Zinc Fingers
8.
Life Sci ; 100(1): 61-6, 2014 Mar 28.
Article En | MEDLINE | ID: mdl-24530740

AIMS: This experiment investigated the effects of sub-chronic aluminum chloride (AlCl3) exposure on rat ovaries. MAIN METHODS: Eighty female Wistar (5weeks old) rats, weighed 110-120g, were randomly divided into four treatment groups: control group (CG), low-dose group (LG, 64mg/kg BW AlCl3), mid-dose group (MG, 128mg/kg BW AlCl3) and high-dose group (HG, 256mg/kg BW AlCl3). The AlCl3 was administered in drinking water for 120days. The ovarian ultrastructure was observed. The activities of acid phosphatase (ACP), alkaline phosphatase (ALP), succinate dehydrogenase (SDH), Na(+)-K(+)-ATPase, Mg(2+)-ATPase and Ca(2+)-ATPase, the contents of Fe, Cu and Zn, and the protein expression of follicle-stimulating hormone receptor (FSHR) and luteinizing hormone receptor (LHR) in the ovary were determined. KEY FINDINGS: The results showed that the structure of the ovary was disrupted, the activities of ALP, ACP, SDH, Na(+)-K(+)-ATPase, Mg(2+)-ATPase and Ca(2+)-ATPase, the contents of Zn, Fe and the protein expression of FSHR and LHR were lowered, and the content of Cu was increased in AlCl3-treated rats than those in control. SIGNIFICANCE: The results indicate that sub-chronic AlCl3 exposure caused the damage of the ovarian structure, the disturbed metabolism of Fe, Zn and Cu and the decreased activities of Na(+)-K(+)-ATPase, Mg(2+)-ATPase and Ca(2+)-ATPase in the ovary, which could result in suppressed energy supply in the ovary. A combination of suppression of energy supply and reduction of expression of FSHR and LHR could inhibit ovulation and corpus luteum development, leading to infertility in female rats.


Aluminum Compounds/toxicity , Chlorides/toxicity , Ovary/drug effects , Acid Phosphatase/metabolism , Alkaline Phosphatase/metabolism , Aluminum Chloride , Animals , Copper/metabolism , Female , Infertility, Female/chemically induced , Iron/metabolism , Ovary/metabolism , Ovary/pathology , Rats , Rats, Wistar , Receptors, FSH/metabolism , Receptors, LH/metabolism , Zinc/metabolism
9.
Neuroscience ; 218: 196-205, 2012 Aug 30.
Article En | MEDLINE | ID: mdl-22609933

Studies have shown a few cerebral metabolites modified by cocaine in brain regions; however, endogenous metabolic profiling has been lacking. Ex vivo (1)H NMR (hydrogen-1 nuclear magnetic resonance) spectroscopy-based metabonomic approach coupled with partial least squares was applied to investigate the changes of cerebral metabolites in nucleus accumbens (NAc) and striatum of rats subjected to cocaine treatment. Our results showed that both single and repeated cocaine treatment can induce significant changes in a couple of cerebral metabolites. The increase of neurotransmitters glutamate and gamma-amino butyric acid (GABA) were observed in NAc and striatum from the rats repeatedly treated with cocaine. Creatine and taurine increased in NAc whereas taurine increased and creatine decreased in striatum after repeated cocaine treatment. Elevation of N-acetylaspartate in NAc and striatum and decrease of lactate in striatum were observed, which may reflect the mitochondria dysregulation caused by cocaine; moreover, alterations of choline, phosphocholine and glycerol in NAc and striatum could be related to membrane disruption. Moreover, groups of rats with and without conditioned place preference (CPP) apparatus are presenting difference in metabolites. Collectively, our results provide the first evidence of metabonomic profiling of NAc and striatum in response to cocaine, exhibiting a regionally-specific alteration patterns. We find that repeated cocaine administration leads to significant metabolite alterations, which are involved in neurotransmitter disturbance, oxidative stress, mitochondria dysregulation and membrane disruption in brain.


Cocaine/pharmacology , Corpus Striatum/drug effects , Corpus Striatum/metabolism , Dopamine Uptake Inhibitors/pharmacology , Nucleus Accumbens/drug effects , Nucleus Accumbens/metabolism , Animals , Magnetic Resonance Spectroscopy , Male , Metabolomics/methods , Rats , Rats, Wistar
10.
J Int Med Res ; 39(5): 1870-5, 2011.
Article En | MEDLINE | ID: mdl-22117988

Globally, prostate cancer is the most common malignancy among men and there is no biomarker for defining tumour invasion and progression. Guanosine-5'-triphosphate (GTP)-binding RAS-like 3 (ARHI) is a tumour suppressor gene that has been found to be downregulated in the prostate cancer cell line PC-3. MicroRNA 221 and 222 have been shown to regulate ARHI expression negatively. This study evaluated tissue samples from patients with prostate cancer (n = 35) that were designated as aggressive or non-aggressive according to their Gleason grade. Expression of ARHI and microRNA 221 and 222 was measured by real-time reverse transcription-polymerase chain reaction. The level of ARHI mRNA was significantly lower in aggressive compared with non-aggressive prostate cancer tissue samples. In contrast, microRNA 221 and 222 levels were significantly higher in aggressive compared with non-aggressive prostate cancer tissue samples. Whether ARHI and microRNA 221 and 222 could be considered as biomarkers for disease progression in prostate cancer requires further investigation.


Biomarkers, Tumor/metabolism , Gene Expression , MicroRNAs/metabolism , Prostatic Neoplasms/metabolism , rho GTP-Binding Proteins/metabolism , Adult , Aged , Aged, 80 and over , Biomarkers, Tumor/genetics , Gene Expression Regulation, Neoplastic , Humans , Male , MicroRNAs/genetics , Middle Aged , Neoplasm Grading , Prostatic Neoplasms/genetics , Prostatic Neoplasms/pathology , rho GTP-Binding Proteins/genetics
11.
J Viral Hepat ; 18(10): e583-90, 2011 Oct.
Article En | MEDLINE | ID: mdl-21914080

The aim of this study was to further investigate the prevalence of infection and genotype of hepatitis E virus (HEV) among different species of animals, people whose works are related to pigs and the general population in the suburb of Beijing, China. Serum and faecal samples were collected from 10 animal species and humans. Anti-HEV was detected by enzyme immunoassays (EIA); HEV RNA was amplified by reverse transcription-nested polymerase chain reaction (RT-nPCR) method. PCR products were cloned and sequenced. The isolated swine HEV sequences were analysed phylogenetically. The positive rates of serum anti-HEV in swine, cattle, milk cow, horse, sheep, donkey, dog, duck, chicken, pig farm workers and slaughterhouse workers, and general population were 81.17% (802/988), 25.29% (66/261), 14.87% (40/269), 14.29% (40/280), 9.30% (53/514), 0 (0/25), 0 (0/20), 2.53% (8/316), 3.03% (7/231), 58.73% (37/63), 35.87% (66/184) and 20.06% (538/2682), respectively. The anti-HEV prevalence in adult swine (≥ 6 months) and younger swine (≤ 3 months) was 91.49% (591/646) and 61.7% (211/342), respectively. The positive rate of HEV RNA in young swine faeces was 47.94% (93/194). All 93 isolates from the younger swine shared 87.8-100% nucleotide homology with each other and had identities of 75.6-78.9%, 73.9-76.1%, 76.4-80.6% and 83.1-95.0% with the corresponding regions of genotypes 1-4 HEV, respectively. Phylogenetic analysis showed that all HEV isolates belong to genotype 4, subgenotype 4d. These results suggest a potential risk of zoonotic transmission of HEV from younger swine to farmers who rear pigs.


Hepatitis E virus/classification , Hepatitis E/transmission , Hepatitis E/veterinary , Swine Diseases/epidemiology , Swine Diseases/transmission , Zoonoses/epidemiology , Zoonoses/transmission , Adult , Animals , Animals, Domestic , China/epidemiology , Cluster Analysis , Feces/virology , Female , Hepatitis Antibodies/blood , Hepatitis E/epidemiology , Hepatitis E virus/genetics , Hepatitis E virus/isolation & purification , Humans , Immunoenzyme Techniques , Male , Molecular Sequence Data , Phylogeny , Polymerase Chain Reaction , RNA, Viral/blood , Reverse Transcriptase Polymerase Chain Reaction , Sequence Analysis, DNA , Serum/virology , Swine , Swine Diseases/virology
12.
Health Commun ; 26(2): 185-97, 2011 Mar.
Article En | MEDLINE | ID: mdl-21318917

Past studies on the efficacy of participation in online cancer support groups have primarily focused on the role of expression in the accrual of health benefits for participants. Unfortunately, few steps have been taken to determine whether this observed effect arises solely from the internal mental processes underlying the act of expressing or, perhaps, owes something to a nuanced, multidimensional understanding of expression that includes reception of responses to what is expressed. To test for the multilayered effect, we attend to one of the key concepts in the online support community scholarship: empathy. Our findings suggest that it is a combination of empathy expression and reception that is crucial to attaining optimal benefits for cancer patients. Further, our finding supports the buffering hypothesis that empathic expression provides a salutary effect for patients who experienced a higher degree of concern associated with their cancer diagnosis and follow-up treatments.


Attitude to Health , Breast Neoplasms/psychology , Self-Help Groups , Communication , Empathy , Female , Humans , Internet , Social Support
13.
J Viral Hepat ; 18(9): 661-7, 2011 Sep.
Article En | MEDLINE | ID: mdl-20609076

UNLABELLED: A novel genotype of hepatitis E virus (HEV) isolated from rabbits is reported. The aim of this study was to confirm and further investigate the prevalence of the novel HEV genotype in rabbits in China. Sera and faecal samples were collected from farmed rex rabbits in Beijing, China. All serum samples were tested for anti-HEV antibody by EIA. Both the serum and the faecal samples were evaluated for detection of HEV RNA using a nested RT-PCR assay. The nucleotide sequences of rabbit HEV were then analysed, and sequence homology of rabbit HEV compared against human HEV genotypes 1-4, and avian HEV. RESULTS: The prevalence of positive serum anti-HEV from rex rabbits was 54.62% (65/119). The detection rate of HEV RNA using ORF2 primers was 6.96% (8/115) amongst rabbit faecal samples. All eight amplicons shared 98.3-100% nucleotide homology with each other and had identities of 75.8-78.6%, 73.9-75.0%, 77.5-81.0%, 74.2-78.6% and 54.8-57.6% with the corresponding regions of genotypes 1-4 and avian HEV, respectively. Phylogenetic analysis showed that the eight sequences formed one individual branch and were on the same branch with GDC9 and GDC46, both of which were reported to be a novel genotype of HEV isolated from rabbits. The conclusion is that this study provides further information about HEV infecting rabbits, which may be a new animal host of HEV, as well as genetical evidence of a new mammalian genotype of HEV.


Hepatitis Antibodies/blood , Hepatitis E virus/genetics , Hepatitis E/veterinary , Viral Proteins/genetics , Animals , China/epidemiology , Feces/virology , Genotype , Hepatitis E/epidemiology , Hepatitis E/immunology , Hepatitis E virus/classification , Hepatitis E virus/immunology , Hepatitis E virus/isolation & purification , Humans , Phylogeny , Prevalence , RNA, Viral/genetics , Rabbits , Reverse Transcriptase Polymerase Chain Reaction/methods , Sequence Homology, Nucleic Acid
14.
Milbank Q ; 86(3): 481-513, 2008 Sep.
Article En | MEDLINE | ID: mdl-18798887

CONTEXT: Raising public awareness of the importance of social determinants of health (SDH) and health disparities presents formidable communication challenges. METHODS: This article reviews three message strategies that could be used to raise awareness of SDH and health disparities: message framing, narratives, and visual imagery. FINDINGS: Although few studies have directly tested message strategies for raising awareness of SDH and health disparities, the accumulated evidence from other domains suggests that population health advocates should frame messages to acknowledge a role for individual decisions about behavior but emphasize SDH. These messages might use narratives to provide examples of individuals facing structural barriers (unsafe working conditions, neighborhood safety concerns, lack of civic opportunities) in efforts to avoid poverty, unemployment, racial discrimination, and other social determinants. Evocative visual images that invite generalizations, suggest causal interpretations, highlight contrasts, and create analogies could accompany these narratives. These narratives and images should not distract attention from SDH and population health disparities, activate negative stereotypes, or provoke counterproductive emotional responses directed at the source of the message. CONCLUSIONS: The field of communication science offers valuable insights into ways that population health advocates and researchers might develop better messages to shape public opinion and debate about the social conditions that shape the health and well-being of populations. The time has arrived to begin thinking systematically about issues in communicating about SDH and health disparities. This article offers a broad framework for these efforts and concludes with an agenda for future research to refine message strategies to raise awareness of SDH and health disparities.


Community Health Services/organization & administration , Health Promotion/organization & administration , Health Status Disparities , Medically Underserved Area , Minority Groups/statistics & numerical data , Primary Health Care/organization & administration , Social Marketing , Communication , Community-Institutional Relations , Health Services Accessibility/organization & administration , Humans , Socioeconomic Factors , United States/epidemiology
15.
Zhonghua Liu Xing Bing Xue Za Zhi ; 19(4): 208-10, 1998 Aug.
Article Zh | MEDLINE | ID: mdl-10322672

Questionnaires were sent through mail to study the epidemiology of drowning in 56 towns and townships in Wujin. Results showed that the prevalence of drowning in Wujin reached 11.14 per 10(5) of which the males out-numbered females. Children aged 1-9 years and people above 60 years old were more than the other age groups. The main causes were due to accidental falls in elderly, children swimming in waters, followed by falling into the river as the result of disease fulmination and suicidal among adults. Measures should be taken to strengthen the care of children, people with mental diseases and the elderly.


Drowning/epidemiology , Adolescent , Adult , Age Factors , Aged , Child , Child, Preschool , China/epidemiology , Drowning/etiology , Female , Humans , Infant , Male , Middle Aged , Prevalence , Surveys and Questionnaires
16.
Anal Chem ; 69(13): 2485-95, 1997 Jul 01.
Article En | MEDLINE | ID: mdl-21639384

An improved inverse gas chromatographic method involving the use of a mass-specific detector for the determination of the glass transition temperature of polymeric materials is described. The new method allows the use of several probe solutes simultaneously with an automated, closed-loop injector and stepped temperature programming. The result is a single continuous chromatogram for each probe solute over a range of temperatures encompassing the glass transition temperature, T(g). Several different methods for the exact determination of T(g) from the chromatogram were investigated, including the classical van't Hoff-type plots with retention volumes calculated from both the peak maximum and first moment values of the elution peaks. Two new methods are also proposed for the evaluation of T(g) from either the temperature dependence of the second moments of the elution peaks for probe solutes or simple inspection of the variation of elution peak height (width) with temperature. All four methods for the determination of T(g) are evaluated with three probe solutes and four different polymers, viz., poly(methyl methacrylate), poly(ethylene terephthalate), polycarbonate, and two batches of polystyrene with different molecular weights and T(g) values. Three phenomenological models were used to interpret the chromatographic retention mechanisms of the solute probes in glassy and rubbery polymers. These are (i) the classical adsorption/absorption model for glass and rubber polymers, (ii) the single absorption mechanism model, and (iii) a dual-mode model previously used to explain the sorption of gases, such as CO(2), in glassy polymers. It is concluded that no single approach is adequate to interpret the experimental results for all of the systems, although each model is adequate for some individual solute/polymer combinations.

17.
Mol Chem Neuropathol ; 17(1): 51-63, 1992 Aug.
Article En | MEDLINE | ID: mdl-1326973

Kainic acid (KA) is a known potent neuroexcitotoxin, although the biochemical mechanism producing its underlying neurotoxic effect is not quite clear. Histopathological examination of gerbil brains 24 h after systemic injection of KA revealed severe neuronal lesions in different regions of the brain, especially the cerebellar and hippocampal areas. We have detected free radical formation in the brain 1 h after KA administration by using an in vivo spin trapping technique. We have also observed increased lipid peroxidation in the brain after KA-treatment by analyzing thiobarbituric acid reactive substances and conjugated diene formation. Diminished brain specific (Na+, K+)-ATPase activity was also found 2 h after KA injection and persisted to 24 h. It is possible that the free radical reaction is a primary cause of neuronal degeneration after KA administration.


Brain Chemistry/drug effects , Kainic Acid/toxicity , Nervous System Diseases/chemically induced , Animals , Free Radicals , Gerbillinae , Histocytochemistry , Lipid Peroxidation/drug effects , Malondialdehyde/metabolism , Nervous System Diseases/pathology , Neurons/drug effects , Sodium-Potassium-Exchanging ATPase/metabolism , Synaptosomes/enzymology , Thiobarbituric Acid Reactive Substances
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