Exploration and Practice of Electronic, Networked and Intelligent Methods for Basic Medical Science Education to Develop Pathology Interest

Introduction/Objective

In response to the sudden COVID-19 pandemic, the Chinese government has restricted student visas for international students as part of an emergency "zero COVID" plan. As a result of these border closures, most international students enrolled in Chinese medical universities have not returned to campus for more than 2.5 years and have continued their medical education online. Basic medical science study has continued relatively smoothly compared to clinical apprenticeships, which focus more on clinical traineeship and practice. How to turn the crisis caused by the pandemic into an opportunity to improve the level of basic medical science education and level of pathology interest in our school is the topic explored in this paper.

Methods/Case Report

The methods proposed in this study include the intelligence of artificial intelligence technology and adaptive teaching tools for teaching students in accordance with their aptitude, interactive microscopic slides and gross pathology recognition methods based on computer graphics technology, and Internet-based group learning and large group discussions. All the advantages of traditional classroom teaching are therefore included and some overcome the shortcomings of traditional classroom teaching.

Results (if a Case Study enter NA)

Grades in 2019-2020 school year basic medical science courses were obtained. In this school year, the first semester was traditional education on campus and the second semester was online using the method described in this paper. Second semester grades were 17.2% higher than the first. USMLE Step 1 performance was another measured outcome because it focuses on basic science and pathology. A good outcome on this exam was obtained and the teaching method proposed in this paper is verified.

Conclusion

The author is preparing to expand the sample size to further verify, improve, and perfect the method proposed in this paper, so as to promote the depth and breadth of basic medical education and continuing success from education into success in pathology careers.

[Pathogenic detection and molecular tracing of a bacillary dysentery outbreak by Shigella sonnei in Huainan city]

Objective: To understand the virulence gene and drug resistance profile of Shigella sonnei outbreak in Huainan city, and conduct pathogenic traceability analysis. Methods: Water samples and feces related to an infectious diarrhea outbreak in Huainan city in August 2020 were collected for multiple pathogen detection. Virulence gene, drug sensitivity, pulse-field gel electrophoresis and whole genome sequencing of Shigella isolates were analyzed respectively. Results: 38 strains of Shigella sonnei were detected in 56 samples of mucilage feces with a positive rate 67.86%, and all serotypes were Shigella sonnei Phase I. Three strains of Shigella sonnei were detected by fluorescence PCR in the Gram-negative (GN) bacterial enrichment solution of terminal water and well water. Virulence genes were ipaH positive (38), ipaH/ial (31) and ipaH/ial/sen positive (1), respectively. The drug resistance spectrum showed that 9 of 14 antibiotics were 100% resistant, and only imipenem, chloramphenicol, ceftazidime and ciprofloxacin were effective drugs. XbaⅠ restriction enzyme map type of 36 isolates was completely consistent, and the ST type analysis of 3 strains was ST152. Whole genome sequencing and analysis verified that the outbreak was caused by a single clonal group of strains, and revealed that the isolates of the outbreak were clustered into a large cluster with 3 Chinese strains and 1 Korean strain in the database, far away from the strains of other countries. Conclusion: The outbreak is caused by a single clone of Shigella sonnei, which are low virulence strains and have multiple drug resistance.

[CD7 expression and its prognostic significance in acute myeloid leukemia patients with wild-type or mutant CEBPA]

目的

分析CD7在初治急性髓系白血病（AML）患者中的表达和预后价值，进一步探讨CD7表达情况与CEBPA突变的相关性，明确其在CEBPA野生型和突变型AML患者中与预后的关系。

方法

回顾性分析2010年1月至2016年12月收治的298例初治AML患者（除外M₃亚型）的临床资料，在全部患者以及CEBPA野生型和突变型组中，分别比较CD7阳性（CD7⁺）和CD7阴性（CD7⁻）患者的临床特征及预后差异，并联合CD7表达情况和CEBPA突变状态初步建立新的危险分层模型。

结果

在CD7⁺组中，CEBPA单位点和双位点突变的发生率分别为10.1%和33.9%，显著高于CD7⁻组（5.3%和4.2%），差异具有统计学意义（P=0.000）。在CEBPA野生型患者中，CD7⁺组患者相较CD7⁻组患者完全缓解率低（P=0.001）、复发率高（P=0.023），而两组总生存（OS）期和无病生存（DFS）期差异无统计学意义（P值均>0.05）；在CEBPA突变患者中，CD7⁺组显示有更长的OS期（P=0.019）和DFS期（P=0.010）。根据CD7表达和CEBPA突变与否将AML患者分为三个亚组：CD7⁺伴CEBPA突变组、CD7⁻组和CD7⁺伴CEBPA野生型组。三组患者的3年OS率分别为80.2%、48.0%和30.6%（P<0.001），3年的DFS率分别为74.1%、37.4%和22.2%（P<0.001）。

结论

CD7⁺组中CEBPA突变率显著高于CD7⁻组，CD7⁺在CEBPA野生型组和突变组AML中存在截然相反的预后意义。根据CD7表达情况和CEBPA突变与否建立新的危险分层模型，有助于指导临床个体化治疗。

Dihydroartemisinin inhibits the growth and invasion of gastric cancer cells by regulating cyclin D1-CDK4-Rb signaling

BACKGROUND

Dihydroartemisinin (DHA), a semisynthetic derivative of artemisinin, has a broad range of biological properties, including antitumor activity. However, the mechanisms by which DHA affects the tumorigenesis of gastric carcinoma (GC) are poorly understood.

MATERIAL AND METHODS

The targets of DHA were identified by network pharmacology, and the association of CDK4 with clinicopathological characteristics and prognosis in patients with GC was analyzed by using TCGA data. CCK8, Transwell and flow cytometric analyses, as well as a tumor xenograft model, were used to assess the effects of DHA on the growth and migration of GC cells. qRT-PCR and Western blot analyses were used to determine the effects of DHA on the cyclin D1-CDK4-Rb signaling pathway.

RESULTS

We identified 13 DHA targets and measured their expression of whichCDK4 expression levels were substantially higher in GC tissues than those in adjacent normal tissues, and high CDK4 expression acted as an independent prognostic factor of poor survival in patients with GC. DHA suppressed cell proliferation, migration and invasion in vitro and in vivo and induced G1 phase cell cycle arrest in a dose-dependent manner by regulating cyclin D1-CDK4-Rb signaling.

CONCLUSIONS

DHA inhibits the tumorigenesis and invasion of GC by regulating cyclin D1-CDK4-Rb signaling and may provide therapeutic strategies for the treatment of GC.

[Clinical-pathological analysis of 71 cases of dermatosis papulosa nigra of Han Chinese people]

Objective: To analyze and summarize the clinical-pathological features of dermatosis papulosa nigra of Han Chinese people. Methods: We collected 71 cases of dermatosis papulosa nigra in the Third people's Hospital of Hangzhou Affiliated to Zhejiang Chinese Medical University of Department of Dermatology from January 2010 to January 2019 which were confirmed clinically and pathologically. The clinical and histopathological data of all patients were analyzed and summarized, and relevant literature were reviewed. Results: Among the 71 patients, 51 were female and 25 were male, their average age was (44±13) years, the average age of onset was (39±14) years, and the average time of diagnosis was (65±51) months. The lesions were multiple dark brown papules with smooth surface, and mostly distributed in the chest and abdomen, 46 cases (64.8%), followed by the back and neck. The mean diameter of the lesions was (1.76±0.99) mm. Meanwhile, the initial onset of pruritus was observed in 15 patients. The pathological features of all lesions were similar to seborrheic keratosis. According to pathological classification, there were 49 (69.0%) cases of the acanthotic type, 11(15.5%) cases of the hyperkeratotic type, 6 (8.5%) cases of spiroid type, 4 (5.6%) cases of irritated type, and 1 (1.4%) case of clonal type. Epidermal pigmentation and/or dermal papillary pigmented granules were observed in 56 cases (78.9%), of which 46 cases (64.8%) had basal layer pigmentation. In addition, inflammatory cell infiltration was found in the superficial dermis of lesions of 10 patients (14.1%) with symptom of itching. Conclusion: Dermatosis papulosa nigra of Han Chinese people has some unique clinical and pathological features.

Recognition of Core- and Polymerase-derived immunogenic peptides included in novel therapeutic vaccine by T cells from Chinese chronic hepatitis B patients

Chronic hepatitis B (CHB) is one of the major public health challenges in the world. Due to a strong interplay between specific T-cell immunity and elimination of hepatitis B virus (HBV), efforts to develop novel immunotherapeutics are gaining attention. TG1050, a novel immunotherapy, has shown efficacy in an animal study. To support the clinical development of TG1050 in China, specific immunity to the fusion antigens of TG1050 was assessed in Chinese patients. One hundred and thirty subjects were divided into three groups as CHB patients, HBV spontaneous resolvers, and CHB patients with HBsAg loss after antiviral treatment. HBV-specific T-cell responses to pools of HBV Core or Polymerase genotype D peptides included in TG1050 were evaluated. HBV Core- or Polymerase-specific cells were detected in peripheral blood mononuclear cells (PBMCs) from the different cohorts. The frequencies and intensities of HBV Core-specific immune responses were significantly lower in CHB patients than in HBsAg loss subjects. In CHB patients, a dominant pool derived from Polymerase (Pol1) was the most immunogenic. CHB patients with low viral loads (<10⁶ IU/mL) were more likely to have a positive response specific to the Core peptide pool. Overall, genotype D-derived peptides included in TG1050 could raise broad and functional T-cell responses in PBMCs from Chinese CHB patients infected with genotype B/C isolates. Core-specific immunogenic domains appeared as "hot spots" with the capacity to differentiate between CHB vs HBsAg loss subjects. These observations support the extended application and associated immune monitoring of TG1050 in China.

[The advances in research on precisely inducing retinal ganglion cells from stem cells]

The injury and repair of retinal neurons is a common scientific problem in the occurrence, development and prognosis of neuronal visual impairment. Transplant of retinal ganglion cells (RGCs) differentiated from stem cells opens a new avenue for treatment of glaucoma and optic neuronal degenerative diseases. For the goal to explore the optimal method for RGCs replacement, this review summarizes the current information regarding the classification and application of stem cells, the growth characteristics of RGCs and the precise methods to induce RGCs, and discusses some important issues that need resolving and are related to RGCs transplantation. It is hoped that this article will provide useful theoretical basis for the research of this field. (Chin J Ophthalmol, 2017, 53: 381-385).

[Workplace social capital and intention to stay among Chinese nurses: a structural equation model]

Objective: To explore a model that workplace social capital is associated with intention to stay (ITS) in the nursing profession and that this association is partially mediated by organizational commitment, job satisfaction, and job stress among Chinese nurses. Methods: A cross-sectional, observationalstudy was conducted in Shanghai, China between September and December 2014. Two thousandforty-two nurses from 23 healthcare organizations were recruited for the current study using a two-stage sampling process.Intention to stay, workplace social capital, job satisfaction, organizational commitment, and job stress was measured by validated scale. Measured variable path analysis (MVPA) was used to test their hypothesized relationships. Results: There were significant positive direct effects from workplace social capital (β=0.11, P<0.01) , organizational commitment (β=0.81, P<0.01) and job satisfaction (β=0.03, P<0.01) to ITS, and a negative direct effects from job strain to ITS (β=-0.03, P<0.01) . The model explained 84% of the variability in ITS. Additionally, workplace social capital had significant positive direct effects on organizational commitment (β=0.65, P<0.01) , job satisfaction (β=0.44, P<0.01) and negative direct effects on job strain (β=-0.35, P<0.01) . The indirect effect of social capital to ITS was 0.55. Job satisfaction was positively associated with organizational commitment (r=0.47, P<0.01) , and negtively associated with job stress (r=-0.12, P<0.01) . Job stress was negtively associated with organizational commitment (r=-0.20, P<0.01) . Conclusion: This study suggests that greater workplace social capital may lead to higher ITS in nursing primarily by increasing commitment to the nursing occupation and their job satisfaction and by reducing their sense of job stress.

[Inhibitory effect of quercetin on the biofilm formation of Streptococcus mutans]

OBJECTIVE

To observe the inhibitory effect of quercetin on the biofilm formation of Streptococcus mutans(Sm), to preliminarily reveal the possible underlying mechanisms, and to evaluate the cytotoxicity of quercetion to human dental pulp cells so as to provide the theoretical basis for the application of quercetin in oral biomaterials.

METHODS

Quercetin storage solution was diluted to 0, 3.125, 6.25, 12.5, 25, 50, 100, 200, 400 and 800 mg/L, and added into Sm medium for 4 h and 24 h, crystal violet staining was used to evaluate the biofilm volume. In subsequent detections, three groups were set: control(0 mg/L), 200 mg/L quercetin and 400 mg/L quercetin. Confocal laser scanning microscopy was used to observe the morphology of the biofilm; qPCR for gtfB, gtfC, comD, comE, and luxS were assessed to preliminarily investigate the mechanisms. Finally, the methyl thiazolyl tetrazolium(MTT)test using human dental pulp cells was used to investigate cytotoxicity.

RESULTS

Quercetin could significantly inhibit up to(86.16±0.45)% of the biofilm formation of Sm(Compared with the control group P=0.00)and effectively removed(43.04±0.53)% of the mature biofilm(Compared with the control group P=0.00). Confocal laser scanning microscopy photographs showed that after co-incubated for 24 h, the dense biofilm structures of the experimental group were destroyed by quercetin both at 200 mg/L and 400 mg/L. Quercetin suppressedover 50% of the expression of gtfB, gtfC, comD, comE(compared with the control group P<0.05)and promoted the expression of luxS up to 2.18 ± 0.24 and 2.84 ± 0.26 after 4 h and 24 h, respectively(compared with the control group P<0.05). Quercetin also exhibited acceptable compatibility for human dental pulp cells.

CONCLUSIONS

Quercetin could effectively reduce the biofilm formation of Sm by inhibiting the expression of the related genes, and exhibited no cytotoxicity for human dental pulp cells. Quercetin has good potential to be applied in oral biological materials.

Impact of adherence to GOLD guidelines on 6-minute walk distance, MRC dyspnea scale score, lung function decline, quality of life, and quality-adjusted life years in a Shanghai suburb

We performed a 1-year cluster-randomized field trial to assess the effect of standardized management of chronic obstructive pulmonary disease (COPD) on lung function and quality of life (QOL) measures in patients in China. We used the Global Initiative for Chronic Obstructive Lung Disease (GOLD) treatment guidelines and assessed indexes including pulmonary function, QOL, quality-adjusted life years (QALY), Medical Research Council (MRC) dyspnea scale, 6-min walk distance (6-MWD), number of emergency visits, and frequency of hospitalization. Of a total of 711 patients with chronic cough and asthma, 132 were diagnosed as having COPD and 102 participated in this study [intervention group (N = 47); control group (N = 55)]. We found that adherence to GOLD guidelines had a perceivable impact on 6-MWD, MRC dyspnea scale score, and QOL. The average QALY increased by 1.42/person/year in the intervention group, but declined by 0.95/person/year in the control group. We conclude that standardized management improves disease severity, QOL, and QALY in COPD patients when treatment protocols adhere to GOLD guidelines.

Mutational analysis of positively charged residues in the N-terminal region of the class IIa bacteriocin pediocin PA-1

The significance of positively charged residues for the target cell binding of pediocin PA-1 bacteriocins was studied by site-directed mutagenesis. Most of the charged residues are located in the N-terminal half of the peptide, which is thought to mediate the initial binding of these bacteriocins to their target cells through electrostatic interactions. Mutated peptides in which the positively charged residues were substituted or increased in number were constructed, and some of these peptides exhibited a twofold increase in the bacteriostatic activity. The greatest enhancement was achieved by introduced the positive charges at position 13, their results show the benefits of introducing an additional cationic residue within this patch in the middle of the N-terminal half of pediocin PA-1 bacteriocins. Thus, the presence of additional cationic residues in the N-terminal half influenced the electrostatic binding of this bacteriocin to its target cells and increased the potency of the peptide on the potency of Micrococcus luteus and Staphylococcus aureus.

SIGNIFICANCE AND IMPACT OF THE STUDY

No previous work has systematically examined the N-terminal cationic residues of the pediocin PA-1 for their functional importance or redundancy. In this study, we examined the structure-function relationships of pediocin PA-1 by site-directed mutagenesis. Mutated peptides in which the positively charged residues were substituted and increased in number exhibited a twofold increase in the bacteriostatic activity. This study demonstrated the importance of the cationic patch in the N-terminal half of pediocin PA-1. The cationic residues influenced the electrostatic binding of the bacteriocin to the target cells and had a greater effect on the potency of the peptide towards Micrococcus luteus and Staphylococcus aureus.

Antitumor effect of fructose 1,6-bisphosphate and its mechanism in hepatocellular carcinoma cells

We aimed to investigate the antitumor effect and mechanism of fructose 1,6-bisphosphate (F1,6BP) in a hepatocellular carcinoma cell line. HepG2 cells were treated with different concentrations of F1,6BP alone or in combination with antioxidant N-acetyl-L-cysteine (NAC) or catalase (CAT), and cell proliferation assays were performed. Nuclear morphology was observed by fluorescence microscopy after Hoechst staining, and apoptosis was measured with flow cytometry. Changes in reactive oxygen species (ROS) levels in HepG2 cells were detected by 2',7'-dichlorodihydrofluorescein diacetate (DCFH-DA) staining. A colorimetric assay was adopted to determine the percentage of oxidized glutathione in these cells. CAT and glutathione peroxidase (GSH-Px) mRNA expression levels in HepG2 cells were measured by real-time fluorescence quantitative PCR. HepG2 cell proliferation was significantly inhibited by F1,6BP, accompanied by an increase in intracellular ROS levels and oxidized glutathione. Upregulated apoptosis and characteristic nuclear morphological changes were observed, and the expression of CAT and GSH-Px mRNA was increased after F1,6BP treatment. The antitumor effect of F1,6BP was significantly decreased after pretreatment with NAC and CAT in HepG2 cells. In conclusion, F1,6BP can induce the apoptosis of HepG2 cells. The mechanism involved may be associated with the generation of ROS, especially the production of H2O2.

[Application of umbilical venous catheter combined with peripherally inserted central catheter in very low birth weight infants]

OBJECTIVE

To study the application of umbilical venous catheter (UVC) combined with peripherally inserted central catheter (PICC) in very low birth weight infants (VLBWIs).

METHODS

A retrospective analysis was performed on the VLBWIs in the neonatal intensive care unit who received UVC combined with PICC (catheter group, n=63) or did not receive the catheter treatment (non-catheter group, n=38) to compare the differences in nosocomial infection, weight gain, and length of hospital stay between the two groups.

RESULTS

The rate of nosocomial infection was 17% in the catheter group and 24% in the non-catheter group (P>0.05). Compared with the non-catheter group, the catheter group had a significantly higher weight gain (11.7±2.0 g/kg•d vs 10.6±2.3 g/kg•d; P<0.05) and a significantly shorter length of hospital stay (40±11 days vs 45±14 days; P<0.05). There was no significant difference in the incidence of complications between the two groups.

CONCLUSIONS

Compared with those not receiving catheter treatment, the VLBWIs receiving UVC combined with PICC have a markedly higher weight gain and a markedly shorter length of hospital stay and show a declining trend in the rate of nosocomial infection.

[High-risk factors for parenteral nutrition-associated cholestasis in very low birth weight infants]

OBJECTIVE

To investigate the high-risk factors for parenteral nutrition-associated cholestasis (PNAC), which is the most common complication of parenteral nutrition for infants, in very low birth weight infants (VLBWIs).

METHODS

Retrospective analysis was performed on the clinical and laboratory data of 204 VLBWIs who received parenteral nutrition for over 2 weeks in the neonatal intensive care unit from August 2006 to December 2011. The infants'liver function was evaluated periodically before and after Parenteral nutrition. Univariate analysis and multivariate analysis were performed in the observation (PNAC) and control (without PNAC) groups.

RESULTS

PNAC occurred in 46 (22.5%) of the 204 VLBWIs. Univariate analysis showed that continuous positive airway pressure (CPAP) ventilation, respiration failure, respiratory distress syndrome (RDS), bronchopulmonary dysplasia (BPD) and retinopathy of prematurity (ROP) were significantly increased in the observation group compared with the control group. The observation group had lower birth weights, longer duration of ventilation, later breast feeding beginning, longer duration of fasting, longer duration of parenteral nutrition, and higher cumulated amino acid and lipid emulsion intake. Logistic regression analysis revealed that duration of fasting was a high-risk factor for PNAC (OR=1.115, 95%CI: 1.031-1.207).

CONCLUSIONS

Many risk factors are associated with PNAC. Early enteral nutrition and short duration of parenteral nutrition are helpful in preventing the incidence of PNAC in VLBWIs.

[Using repeated measurement of 'analysis of variance' on hypertension patients to evaluate the self-management program in the communities]

OBJECTIVE

To explore the application of repeated measurement 'analysis of variance' (ANOVA) in evaluating the effectiveness of 'community-based hypertension self-management program'.

METHODS

A community-based parallel controlled trial was conducted among 3 communities. 169 patients in intervention group took part in the course on hypertension self-management program once a week and 204 patients in control group received routine hypertension management services. Data collected through questionnaire at baseline and 6 months, 12 months after intervention and were compared through repeated ANOVA measurement.

RESULTS

Subjects in the intervention group showed statistical significance and linear trends in health self-evaluation, distress, in low spirit, self-efficacy in managing symptoms (SEMS), self-efficacy to managing diseases in general (SEMDG), systolic blood pressure (SBP) and diastolic blood pressure (DBP) over time by univariate test of repeated measurement ANOVA. The score of SEMS increased from 6.84 +/- 2.53 at baseline to 8.20 +/- 1.44 at 12 months after intervention while SEMDG from 7.28 +/- 2.45 to 8.89 +/- 1.05, and SBP decreased from 137.66 +/- 7.30 mm Hg (1 mm Hg = 0.133 kPa) to 130.41 +/- 7.71 mm Hg, DBP decreased from 84.13 +/- 6.70 mm Hg to 81.04 +/- 5.98 mm Hg respectively. Only low spirit and SBP changed over time were seen in the control group. Self-evaluation, distress,in low spirit, caused by diseases, SEMS, SEMDG and SBP were statistically different between control and intervention groups, and the effect of interaction between groups and time span were statistically significant on indicators as self-evaluation, low spirit, self-efficacy in managing symptoms, self-efficacy to manage diseases and SBP etc, by multivariate test of repeated measurement ANOVA.

CONCLUSION

Repeated measurement ANOVA not only could be used to analyze group-effect, but could also explain the effect and the interaction among groups and time, to make the results more reliable. The self-management approach could improve the health status and self-efficacy of the patients,so as to reduce the blood pressure. Our result showed that it was effective for hypertensive patients to be on the chronic diseases self-management program.

Identification of a novel isoform of microsomal triglyceride transfer protein

Microsomal triglyceride transfer protein (MTP) has been studied extensively, primarily because of its role in the assembly of very low density lipoproteins by the liver and chylomicrons by the intestine. Recent studies have suggested that MTP may also play key roles in other cellular processes. In this paper we report the identification of a novel splice variant of MTP in mice. This isoform, MTP-B, has a unique first exon located approximately 2.7 kilobases upstream of canonical MTP (MTP-A) exon 1. The alternative exon encodes 35 amino acids compared with 20 amino acids encoded by exon 1 of MTP-A. MTP-B represents approximately 90% of total MTP mRNA in mouse adipocytes and 3T3-L1 cells and <5% in mouse liver and intestine. Expression of the alternate isoform in mouse liver was confirmed by mass spectrometry. Co-transfection of COS cells with truncated forms of apoB and either MTP-A or MTP-B demonstrated that both isoforms are effective in the assembly and secretion of nascent apoB-containing lipoproteins. Confocal microscopy of 3T3-L1 cells transfected with enhanced green fluorescent protein or DsRed fusions of the two proteins revealed that MTP-A is localized to the endoplasmic reticulum, whereas MTP-B localizes primarily to the Golgi complex in these cells. We conclude that MTP-B functions similarly to MTP-A in lipoprotein assembly. However, in nonlipoprotein-secreting cells, such as the adipocyte, MTP-B may have different localization properties, perhaps reflecting a distinct role in lipid storage and mobilization.

Thermal desorption of hydrogen from carbon nanosheets

Carbon nanosheets are a unique nanostructure that, at their thinnest configuration, approach a single freestanding graphene sheet. Temperature desorption spectroscopy (TDS) has shown that the hydrogen adsorption and incorporation during growth of the nanosheets by radio frequency plasma-enhanced chemical vapor deposition are significant. A numerical peak fitting to the desorption spectra (300-1273 K) via the Polanyi-Wigner equation showed that desorption followed a second order process, presumably by the Langmuir-Hinshelwood mechanism. Six peaks provide the best fit to the TDS spectra. Surface desorption activation energies were determined to be 0.59, 0.63, and 0.65 eV for the external graphite surface layers and 0.85, 1.15, and 1.73 eV for desorption and diffusion from the bulk. In contrast to TDS data from previously studied a-C:H films [Schenk et al. J. Appl. Phys. 77, 2462 (1995)], a greater amount of hydrogen bound as sp(2) hybridized carbon was observed. A previous x-ray diffraction study of these films has shown a significant graphitic character with a crystallite dimension of L(a)=10.7 nm. This result is consistent with experimental results by Raman spectroscopy that show as-grown carbon nanosheets to be crystalline as commercial graphite with a crystallite size of L(a)=11 nm. Following TDS, Raman data indicate that the average crystallite increased in size to L(a)=15 nm.

Physiological relevance of apolipoprotein E recycling: studies in primary mouse hepatocytes

Studies in our laboratory have shown that a fraction of apolipoprotein (apo) E internalized by hepatocytes escapes degradation and is resecreted. Although the intracellular routing is not fully understood, our studies suggest that a portion of apoE recycles through the Golgi apparatus. Given the role of the Golgi apparatus in lipoprotein secretion and the fact that apoE modulates the hepatic secretion of very low-density lipoprotein, we hypothesized that recycling apoE has an effect on hepatic very low-density lipoprotein assembly and/or secretion. To test this hypothesis, apoE-/- mice were transplanted with bone marrow from wild-type mice. In this model, extrahepatic (macrophage-derived) apoE is internalized by the hepatocytes in vivo and is resecreted when the hepatocytes are placed in culture. Unexpectedly, our studies demonstrate that recycling apoE has little effect on hepatic lipid content or hepatocyte triglyceride secretion. In addition, recycling apoE has little effect on the expression of enzymes and proteins involved in lipid synthesis as well as plasma lipoprotein apoproteins. We conclude that the physiological relevance of apoE recycling may not be related to cell-specific functions, such as lipoprotein assembly in the liver. Rather, recycling may provide a mechanism for modulating general cellular effects such as intracellular cholesterol transport or cholesterol efflux.

Direct evidence for predation on trilobites in the Cambrian

A fossil arthropod similar to Fuxianhuia and displaying an exceptionally well-preserved alimentary canal with in situ gut contents is reported from the lower Middle Cambrian (ca. 510 Myr ago) of South China. Three-dimensionally preserved, paired phosphatic nodules, arranged in series along both sides of the gut and containing spherical bacteria, probably represent serial digestive glands. The gut is filled with fragments of the eodiscoid trilobite, Pagetia. The well-developed digestive glands and the fragmentary trilobite remains suggest (i) that the arthropod was a durophagous, possibly selective predator, and (ii) that small trilobites such as eodiscoids were a major food source in Cambrian marine ecosystems. This fossil association augments the small number of previously described associations providing more or less direct evidence of predator-prey relationships in Cambrian epibenthic communities.

Subcellular localization of microsomal triglyceride transfer protein

Microsomal triglyceride transfer protein (MTP) is essential for the assembly of apolipoprotein B-containing lipoproteins. Within the endoplasmic reticulum, it transfers lipid from the membrane to the forming lipoprotein. Recent evidence suggests that it may also function within the Golgi apparatus. To address this hypothesis, we developed a polyclonal antibody to MTP and used it in a series of studies on mouse liver and McArdle-RH7777 (McA) cells. Western blot analysis demonstrated the presence of MTP within mouse hepatic-Golgi apparatus-rich fractions. In addition, in vitro lipid transfer assays demonstrated the presence of triglyceride transfer activity within the Golgi fractions. Immunohistochemical studies with mouse liver demonstrated the presence of MTP within all hepatocytes, but not in nonparenchymal cells. The subcellular location of MTP in McA cells was investigated using confocal microscopy. MTP colocalized with the trans-Golgi network (TGN) 38 and Golgi SNARE (soluble N-ethylmalemide-sensitive factor attachment protein receptor) of 28 kDa (GS28), markers for the trans- and cis-Golgi apparatus, respectively. Morphometric analyses indicated that approximately 17% of the MTP signal colocalized with the TGN38, while 33% of the trans-Golgi marker colocalized with the MTP. Approximately 17% of the MTP signal colocalized with the GS28, whereas 53% of the cis-Golgi marker colocalized with the MTP. The results provide unequivocal evidence for the location of MTP within the Golgi apparatus, and further highlight the importance of this organelle in the assembly of lipoproteins.

The 5'-flanking region of the murine epididymal protein of 17 kilodaltons gene targets transgene expression in the epididymis

A murine epididymal retinoic-acid-binding protein (mE-RABP) is specifically expressed in the mid/distal caput epididymidis and is androgen regulated. The murine epididymal protein of 17 kDa (mEP17) gene, a novel gene homologous to mE-RABP, is located within 5 kb of the 5'-flanking region of the mE-RABP gene. In contrast, expression of the mEP17 gene is restricted to the initial segment and regulated by factor(s) contained in testicular fluid. To identify cis-DNA regulatory element(s) involved in the tissue- and region-specific expression of the mEP17 gene in transgenic mice, we have studied the expression of a transgene containing 5.3 kb of the 5'-flanking region of the mEP17 gene (5.3mEP17) linked to chloramphenicol acetyltransferase (CAT) reporter gene. Significant caput epididymidis-specific CAT activity was detected in transgenic mouse lines; and CAT gene expression is restricted to the initial segment, as is the expression of the endogenous mEP17 gene. Ontogenic expression and testicular factor dependency also mimic that of endogenous mEP17 gene. These results suggest that the 5.3mEP17 fragment contains all the information required for spatial and temporal expression in the mouse epididymis. The 5.3mEP17 fragment will be useful to express a foreign gene of interest in the epididymis in an initial segment-specific manner.

Effects of long-term cigarette smoking on the human locus coeruleus

BACKGROUND

It has been hypothesized that cigarette smoking among subjects with major depression is a form of self-medication. To explore a possible biological basis for this hypothesis, noradrenergic proteins in the locus coeruleus (LC) were measured in long-term cigarette smokers and in nonsmokers. The LC was studied because elevated amounts of alpha2-adrenoceptors and tyrosine hydroxylase have been observed postmortem in the LCs of subjects with major depression or who commit suicide, and because long-term administration of antidepressant drugs to rats down-regulates these proteins in the LC.

METHODS

Postmortem LCs were obtained from long-term cigarette smokers (n=7) and from nonsmokers (n = 9), all of whom lacked diagnoses of major depression. Amounts of tyrosine hydroxylase immunoreactivity and radioligand binding to the norepinephrine transporter, monoamine oxidase A, and alpha2-adrenoceptors were measured.

RESULTS

Amounts of tyrosine hydroxylase immunoreactivity and radioligand binding to alpha2-adrenoceptors were significantly lower (approximately 60% and 40%, respectively) along the axis of the LCs of long-term smokers compared with nonsmokers. Smoking had no statistically significant effects on binding to monoamine oxidase A or to the norepinephrine transporter.

CONCLUSION

This is the first demonstration that cigarette smoking affects noradrenergic proteins in the LC. The direction of these changes is opposite to that observed when comparing subjects who have major depression with normal controls and the same as that produced by long-term antidepressant treatment in animals. If the present observations reflect long-term effects of smoking on premortem noradrenergic biochemistry, smoking-induced changes in LC biochemistry may strengthen the smoking habit among subjects with major depression.

Pregrowth-desiccation: a simple and efficient procedure for the cryopreservation of rice (Oryza sativa L.) embryogenic suspension cells

Rice embryogenic suspension cells were successfully cryopreserved by a pregrowth-desiccation procedure. Cells were precultured in liquid AA medium containing 0.175 mol/L sucrose for 3 d and then in liquid AA medium containing 0.4 mol/L sorbitol for 1 d. After air-drying for about 20 h to a water content of 10%, the cells were placed into cryotubes and quenched into liquid nitrogen. Using this pregrowth-desiccation procedure, a survival rate of 96+/-6% (TTC reduction assay) or 100% (cell clump regrowth) was achieved. Cryostored cells revived very quickly during the recovery culture and they retained the ability to regenerate fertile plants. In conclusion, air-drying, a method usually employed in cryopreservation of seeds or shoot tips, can be used as a simple and efficient procedure for the cryopreservation of precultured rice suspension cells.

Regulation of the human norepinephrine transporter by cocaine and amphetamine

Certain antidepressant and psychostimulant drugs block the uptake of norepinephrine from the synaptic cleft by inhibiting norepinephrine transporter (NET) function. The effects of chronic occupation of the NET by these drugs on NET expression are poorly understood. We previously described down-regulation of the NET in cultured cells after continuous exposure to the tricyclic antidepressant desipramine. Here, the effects of structurally unrelated NET ligands, cocaine and amphetamine, on levels of NET and on NET function in HEK-293 cells transfected with human NET cDNA were investigated. All drug exposures were followed by incubation in drug-free media before harvesting and assays. Exposure of intact cells to cocaine for 3 days did not significantly affect the B(max) or K(D) of [(3)H]nisoxetine binding to NET in membrane homogenates, and did not alter levels of NET immunoreactivity or NET mRNA. In contrast, incubation of cells with amphetamine significantly reduced [(3)H]nisoxetine binding to NET and levels of NET immunoreactivity in a time-dependent manner, although levels of NET mRNA appeared to be unaffected. Exposures to cocaine or amphetamine resulted in significant reductions of [(3)H]norepinephrine uptake, although the magnitude of the reduction produced by amphetamine was much greater than cocaine. [(3)H]Nisoxetine binding to NET and NET protein levels were also reduced by exposure of cells to high concentrations of norepinephrine, although norepinephrine exposures were accompanied by changes indicative of cellular toxicity. Cocaine and amphetamine have distinctly different effects on NET expression after continuous exposure. The ability of only certain drugs to down-regulate the NET may provide clues to the unique therapeutic effects of antidepressants that are NET ligands.

[Present-conditions of nutritional knowledge of clinical doctors]

Nutritional knowledge of 184 clinical doctors was investigated by questionnaires. The results showed that clinical doctors did not have enough nutritional knowledge to meet the demands of their work. The doctors grasped fundamental nutritional knowledge better than clinical nutritional knowledge (P < 0.01). There was no significant difference between the doctors in different groups with different academic degrees, professional titles, work histories, and departments (P > 0.05). Therefore, we suggest that the class hours of nutrition science can be added, the course of clinical nutrition can be offered in medical university, and the nutritional knowledge of clinical doctors can be improved by conducting nutritional science training course.

Elevated levels of tyrosine hydroxylase in the locus coeruleus in major depression

BACKGROUND

Levels of tyrosine hydroxylase (TH) are regulated in the noradrenergic locus coeruleus (LC) in response to changes in the activity of LC neurons and in response to changes in brain levels of norepinephrine. To study the potential role of central noradrenergic neurons in the pathobiology of major depression, TH protein was measured in the LC from postmortem brains of 13 subjects with a diagnosis of major depression and 13 age-matched control subjects having no Axis I psychiatric diagnosis. Most of the major depressive subjects died as a result of suicide.

METHODS

Protein from sections cut through multiple rostro-caudal levels of LC was transferred to Immobilon-P membrane, immunoblotted for TH, and quantified autoradiographically.

RESULTS

The distribution of TH-immunoreactivity (TH-ir) along the rostro-caudal axis of the LC was uneven and was paralleled by a similar uneven distribution of neuromelanin-containing cells in both major depressive and psychiatrically normal control subjects. Amounts of TH-ir in the rostral, middle and caudal levels of the LC from major depressive subjects were significantly higher than that of matched control subjects. There were no significant differences in the number of noradrenergic cells at any particular level of the LC comparing major depressive subjects to control subjects.

CONCLUSIONS

Elevated expression of TH in the LC in major depression implies a premortem overactivity of these neurons, or a deficiency of the cognate transmitter, norepinephrine.

alpha2C adrenoceptors inhibit adenylyl cyclase in mouse striatum: potential activation by dopamine

alpha2C adrenoceptors occur in high density in the striatum, but the functional role of these receptors is uncertain. Mice with targeted inactivation of the alpha2C adrenoceptor gene (Adra2c-/-) and genetically related control mice expressing the wild-type alpha2C adrenoceptor (Adra2c+/+) were used to determine whether striatal alpha2C adrenoceptors modulate adenylyl cyclase activation. In striatal slices from Adra2c+/+ mice, the alpha2 adrenoceptor antagonist RX821002 facilitated forskolin-stimulated cyclic AMP accumulation in a concentration-dependent manner. In contrast, RX821002 had no effect on forskolin-stimulated cAMP accumulation in striatal slices from Adra2c-/- mice or in striatal slices from Adra2c+/+ mice treated with reserpine and alpha-methyl-rho-tyrosine to deplete monoamine neurotransmitters. Given the sparse innervation of the striatum by noradrenergic neurons, the possibility that dopamine can activate the mouse alpha2C adrenoceptor at physiologically relevant concentrations was investigated using normal rat kidney (NRK) cells transfected with the mouse alpha2A or alpha2C adrenoceptor cDNA (NRK-alpha2A or NRK-alpha2C cells). Inhibition of [3H]RX821002 binding by agonists in homogenates of transfected cells revealed an affinity of dopamine for alpha2C adrenoceptors that was higher than the affinity of norepinephrine for its cognate receptor, the alpha2A adrenoceptor. Both norepinephrine and dopamine inhibited forskolin-stimulated cAMP accumulation in intact NRK-alpha2C cells. In NRK-alpha2A cells, norepinephrine facilitated forskolin-stimulated cAMP accumulation, an effect not observed for dopamine. Together, these data demonstrate that the alpha2C adrenoceptor is negatively coupled to adenylyl cyclase and is tonically activated in mouse striatal slices. The endogenous activator of the striatal alpha2C adrenoceptor may be dopamine, as well as norepinephrine.

Interaction of eye protein kinase C and INAD in Drosophila. Localization of binding domains and electrophysiological characterization of a loss of association in transgenic flies

Drosophila eye-specific protein kinase C (eye-PKC) is involved in light adaptation and deactivation. eye-PKC, NORPA (phospholipase Cbeta), and transient-receptor-potential (TRP) (calcium channel) are integral components of a signal transduction complex organized by INAD, a protein containing five PDZ domains. We previously demonstrated the direct association between the third PDZ domain of INAD with TRP in addition to the carboxyl-terminal half of INAD with the last three residues of NORPA. In this work, the molecular interaction between eye-PKC and INAD is defined via the yeast two-hybrid and ligand overlay assays. We show that the second PDZ domain of INAD interacts with the last three residues in the carboxyl-terminal tail of eye-PKC, Thr-Ile-Ile. The association between eye-PKC and INAD is disrupted by an amino acid substitution (Ile-700 to Asp) at the final residue of eye-PKC. In flies lacking endogenous eye-PKC (inaCp215), normal visual physiology is restored upon expression of wild-type eye-PKC, whereas the eye-PKCI700D mutant is completely inactive. Flies homozygous for inaCp209 and InaDp215, a mutation that causes a loss of the INAD-TRP association, were generated. These double mutants display a more severe response inactivation than either of the single mutants. Based on these findings, we conclude that the in vivo activity of eye-PKC depends on its association with INAD and that the sensitivity of photoreceptors is cooperatively regulated by the presence of both eye-PKC and TRP in the signaling complex.

Down-regulation of the human norepinephrine transporter in intact 293-hNET cells exposed to desipramine

The effects of continuous exposure of cultured cells expressing the human norepinephrine transporter (hNET) to the hNET inhibitor desipramine on hNET expression and function were studied. Exposure of HEK-293 cells transfected stably with the hNET cDNA (293-hNET cells) to desipramine for 3 days reduced the specific binding of [3H]nisoxetine in membrane homogenates in a concentration-dependent manner. The magnitude of the reductions in [3H]nisoxetine binding to hNET was dependent on the length of time of the exposure to desipramine, reaching 77% after a 21-day exposure. The reduction of [3H]nisoxetine binding returned to control levels within 72 h after a 3-day exposure to desipramine. Reductions in [3H]nisoxetine binding to hNET were accompanied by time-dependent and exposure concentration-dependent reductions in hNET protein levels as determined by western blotting. Similar to binding, hNET protein levels returned to control levels 72 h after cessation of desipramine exposure. Northern blotting indicated that exposure of 293-hNET cells to desipramine did not significantly alter hNET mRNA levels. Uptake of [3H]norepinephrine by 293-hNET cells was markedly reduced after a 3-day exposure to desipramine. However, desipramine exposure had no effect on uptake of [3H]glutamate or [3H]alanine. The present findings imply that down-regulation of the hNET in 293-hNET cells induced by desipramine results from a selective reduction in hNET protein levels, presumably a consequence of either a reduction in the translation of hNET mRNA or from an enhanced degradation of hNET protein.

Association of INAD with NORPA is essential for controlled activation and deactivation of Drosophila phototransduction in vivo

Visual transduction in Drosophila is a G protein-coupled phospholipase C-mediated process that leads to depolarization via activation of the transient receptor potential (TRP) calcium channel. Inactivation-no-afterpotential D (INAD) is an adaptor protein containing PDZ domains known to interact with TRP. Immunoprecipitation studies indicate that INAD also binds to eye-specific protein kinase C and the phospholipase C, no-receptor-potential A (NORPA). By overlay assay and site-directed mutagenesis we have defined the essential elements of the NORPA-INAD association and identified three critical residues in the C-terminal tail of NORPA that are required for the interaction. These residues, Phe-Cys-Ala, constitute a novel binding motif distinct from the sequences recognized by the PDZ domain in INAD. To evaluate the functional significance of the INAD-NORPA association in vivo, we generated transgenic flies expressing a modified NORPA, NORPAC1094S, that lacks the INAD interaction. The transgenic animals display a unique electroretinogram phenotype characterized by slow activation and prolonged deactivation. Double mutant analysis suggests a possible inaccessibility of eye-specific protein kinase C to NORPAC1094S, undermining the observed defective deactivation, and that delayed activation may similarly result from NORPAC1094S being unable to localize in close proximity to the TRP channel. We conclude that INAD acts as a scaffold protein that facilitates NORPA-TRP interactions required for gating of the TRP channel in photoreceptor cells.

Down-regulation of norepinephrine transporters on PC12 cells by transporter inhibitors

To investigate the regulation of norepinephrine transporters (NETs) in vitro, we measured the binding of the NET-selective ligand [3H]nisoxetine in homogenates of PC12 cells after exposure of intact cells to the NET inhibitor desipramine (DMI). A 3-day exposure of PC12 cells to DMI robustly reduced the Bmax, but not the KD, of [3H]nisoxetine binding to NETs. Reduction of the binding of [3H]nisoxetine was dependent on both the concentration of DMI and the time of exposure to DMI. Reduction of [3H]nisoxetine binding to NETs produced by a 1-day exposure to DMI reverted to preexposure levels 48 h after cessation of DMI exposure. Similar down-regulation of NETs was found when PC12 cells were exposed to another NET-selective drug, nisoxetine, which is structurally unrelated to DMI. In contrast, exposure of cells to the serotonin transporter-selective drug citalopram, or the NET substrate norepinephrine, had no effects on the binding of [3H]nisoxetine to NETs. The down-regulation of NETs was paralleled by a DMI-induced reduction in the uptake of [3H]norepinephrine in intact PC12 cells. It can be inferred from these data that inhibitors of the NET can down-regulate NETs directly, and do so in the absence of changes in the synaptic concentration of norepinephrine.

Regulation of the TRP Ca2+ channel by INAD in Drosophila photoreceptors

Drosophila vision involves a G protein-coupled phospholipase C-mediated signaling pathway that leads to membrane depolarization through activation of Na+ and Ca2+ channels. InaD mutant flies have a M442K point mutation and display a slow recovery of the Ca2+ dependent current. We report that anti-INAD antibodies coimmunoprecipitate TRP, identified by its electrophoretic mobility, cross reactivity with anti-TRP antibody, and absence in a null allele trp mutant. This interaction is abolished by the InaD point mutation in vitro and in vivo. Interaction was localized to the 19 amino acid C-terminus of TRP by overlay assays, and to the PDZ domain of INAD, encompassing the point mutation. Given the impaired electrophysiology of the InaD mutant, this novel interaction suggests that INAD functions as a regulatory subunit of the TRP Ca2+ channel.

Aromatic L-amino acid decarboxylase: biological characterization and functional role

1. Aromatic L-amino acid decarboxylase is the enzyme responsible for the decarboxylation step in both the catecholamine and the indolamine synthetic pathways. Immunological and molecular biological studies suggest that it is a single enzyme with one catalytic site but with different locations for attachment of the substrates. The enzyme is widely distributed in the brain and in peripheral tissues. 2. Recent investigations have shown that the enzyme is regulated by short term mechanisms that may involve activation of adenyl cyclase or protein kinase C. In addition, a long-term mechanism of activation by altered gene expression has also been suggested.

[Changes of cytoplasmic calcium and magnesium concentration and calcium distribution in human platelets caused by thrombin]

Changes of calcium and magnesium concentration in human platelets during thrombin induced agglutination and the distribution of the respective concentration in the platelet population were measured by fluorescence probe using fura 2, mag-fura 2 and fluo 3. The cytoplasmic free calcium concentration increases with addition 2 thrombin. When the thrombin concentration was increased to 0.5 U/ml, the calcium concentration increase showed two rising peaks. The popular cytoplasmic calcium concentration in platelets shows normal distribution. The cytoplasmic free magnesium concentration also increases with increase of calcium concentration, showing that magnesium also plays a significant effect in the condensation of platelets.

The effects of administration of monoamine oxidase-B inhibitors on rat striatal neurone responses to dopamine

1. (-)-Deprenyl has been shown to potentiate rat striatal neurone responses to dopamine agonists at doses not altering dopamine metabolism. Since there are a number of effects of (-)-deprenyl which could result in this phenomenon, we have investigated the effects of MDL 72,145 and Ro 19-6327, whose only common effect with (-)-deprenyl is an inhibition of monoamine oxidase-B (MAO-B), on rat striatal neurone responses to dopamine and on striatal dopamine metabolism. 2. Using in vivo electrophysiology, i.p. injection of either MDL 72,145 or Ro 19-6327 was found to produce a dose-dependent potentiation of striatal neurone responses to dopamine but not gamma-aminobutyric acid. 3. Neurochemical investigations revealed that this occurred at doses (0.25-1 mg kg-1) which, while not affecting levels of dopamine or its metabolites, 3,4-dihydroxyphenylacetic acid or homovanillic acid, did cause a significant, dose-dependent, elevation in striatal levels of the putative neuromodulator, 2-phenylethylamine (PE). 4. Inhibition of PE synthesis by i.p. injection of the aromatic L-amino acid decarboxylase inhibitor, NSD 1015, produced a reversal of the effects of MDL 72,145 and Ro 19-6327. 5. Neurochemical analysis revealed this to occur at a dose of NSD 1015 (10 mg kg-1) selective for reduction of elevated PE levels. 6. These results suggest that PE can act as a neuromodulator of dopaminergic responses and that MAO-B inhibitors may potentiate neuronal responses to dopamine via the indirect mechanism of elevation of PE following MAO-B inhibition.

Regulation of aromatic L-amino acid decarboxylase in rat striatal synaptosomes: effects of dopamine receptor agonists and antagonists

1. In this study we investigated the effects of dopamine receptor agonists and antagonists on rat striatal synaptosomal aromatic L-amino acid decarboxylase (AADC) activity. 2. The results show that 10(-5)-10(-7) M cis-flupenthixol increased the striatal synaptosomal AADC activity (by 25% to 57%) in a time-dependent manner. SCH 23390 and remoxipride alone had little or no effect on striatal synaptosomal AADC activity, but in combination they increased AADC activity by 20%, suggesting that the increases in striatal synaptosomal AADC activity occurred only after blockade of both dopamine D1 and D2 receptors. 3. Treatment with (+)-amphetamine and (+/-)-2-(N-phenylethyl-N-propyl)amino-5- hydroxytetralin hydrochloride ((+/-)-PPHT) produced a reduction of striatal synaptosomal AADC activity in a concentration- and time-dependent manner. SKF 38393 and (-)-quinpirole, however, exhibited no effect on striatal synaptosomal AADC activity, suggesting that only the mixed dopamine receptor agonists can reduce the AADC activity. Incubation with apomorphine at a concentration of 10(-4) M inhibited the AADC activity by 74% and this inhibition cannot be antagonized by SCH 23390, remoxipride or cis-flupenthixol, suggesting that apomorphine-induced inhibition of striatal synaptosomal AADC activity was not mediated by dopamine receptors. 4. cis-Flupenthixol can reverse the reduction of AADC activity induced by (+)-amphetamine and (+/-)-PPHT. The inhibition of AADC activity elicited by (+/-)-PPHT also can be reversed by SCH 23390 and remoxipride. 5. The inhibition of striatal synaptosomal AADC activity induced by (+/-)-PPHT is calcium-dependent and protein kinase C may play a role in the regulation of striatal AADC activity. 6. These studies show that striatal synaptosomal AADC activity is regulated by dopamine receptors and indicate that in vitro dopamine DI and D2 receptors have a synergistic effect in this regulation.

Dopamine metabolism in the guinea pig striatum: role of monoamine oxidase A and B

These studies were carried out to determine whether the greater abundance of monoamine oxidase B in the guinea pig affects the actions of (-)-deprenyl on dopamine metabolism in whole tissue or in extracellular fluid. The administration of (-)-deprenyl in doses that do not affect monoamine oxidase A activity (1-4 mg kg-1, 2 h) increases striatal 2-phenylethylamine and dopamine concentrations and reduces 3,4-dihydroxyphenylacetic acid. No effects were observed on striatal homovanillic acid, 5-HT and 5-hydroxyindole acetic acid. Inhibition of monoamine oxidase A with clorgyline with doses up to 8 mg kg-1 (2 h) does not affect striatal 2-phenylethylamine but increases dopamine and 5-HT concentrations and reduces 3,4-dihydroxyphenyl-acetic acid and 5-hydroxyindole acetic acid. (-)-Deprenyl (2-4 mg kg-1) did not change the extracellular concentrations of dopamine but the higher dose produced a limited reduction in extracellular 3,4-dihydroxyphenylacetic acid. Inhibition of monoamine oxidase A and monoamine oxidase B with pargyline (75 mg kg-1, 2 h) significantly increased the levels of extracellular dopamine and reduced those of their acid metabolites. These results show that in the guinea pig striatum inhibition of monoamine oxidase B by (-)-deprenyl impairs the metabolism of dopamine in the whole tissue but does not produce a marked increase in extracellular dopamine.

Regulation of striatal aromatic L-amino acid decarboxylase: effects of blockade or activation of dopamine receptors

Previous experiments have shown that blockade of dopamine D1 or D2 receptors by SCH 23390 or pimozide increases aromatic L-amino acid decarboxylase (AADC) activity in the rat striatum and the mesolimbic system. This study examined whether other dopamine receptor antagonists affect AADC activity and if there is an interaction between dopamine D1 and D2 receptor blockade on AADC activity. The possible effect of dopamine receptor agonists on AADC activity has been investigated as well. Administration of cis-flupenthixol (0.5 and 1 mg/kg) increased striatal AADC activity (by 25 and 26% above controls) and similar effects were observed with remoxipride (0.5-4 mg/kg) (by 18-27% above controls). Pretreatment with cycloheximide (10 mg/kg) did not change the increases produced by cis-flupenthixol (0.5 mg/kg). The administration of non-neuroleptic trans-flupenthixol did not change AADC activity. Combined treatment with SCH 23390 (0.1 mg/kg) and remoxipride (0.5 mg/kg), but not combination of SCH 23390 (0.1 mg/kg) and pimozide (0.3 mg/kg), showed higher increases of AADC activity than by the individual treatments, suggesting an interaction between the effects of the two drugs. Bromocriptine, but not (-)-quinpirole and d-amphetamine, significantly reduced the striatal AADC activity by 23% at the dose of 10 mg/kg. The results further demonstrate that AADC is a regulated enzyme in the rat brain.

Specific irreversible monoamine oxidase B inhibitors stimulate gene expression of aromatic L-amino acid decarboxylase in PC12 cells

The effect of some selective monoamine oxidase (MAO) inhibitors on aromatic L-amino acid decarboxylase (AADC) gene expression in PC12 cells has been examined. Irreversible MAO B inhibitors [(-)-deprenyl, pargyline, and MDL 72,974A] stimulated AADC gene expression, whereas a selective irreversible MAO A inhibitor (clorgyline) and a reversible MAO B inhibitor (Ro 19-6327) had no effect. Because there is no apparent MAO B activity in PC12 cells, it is postulated that there is a novel site of action for these MAO B inhibitors and that the pharmacological profile of this site matches that of neuroprotective MAO B inhibitors. Finally, it is suggested that the stimulation of AADC gene expression may be relevant to the antiparkinsonian effects of MAO B inhibitors.

Gene expression of aromatic L-amino acid decarboxylase in cultured rat glial cells

Northern blot hybridization was performed to detect aromatic L-amino acid decarboxylase (AADC) mRNA in primary cultures of astrocytes and C6 glioma cells. The cDNA probe for rat AADC was generated by reverse transcription from rat adrenal gland total RNA and was amplified by the polymerase chain reaction method. AADC mRNA from cultured astrocytes and C6 glioma cells was present as a single band, 2.2 kbp in size, that comigrated with the RNA from rat kidney. Western immunoblot showed a single protein band at 52 kDa for AADC enzyme protein. These findings demonstrate that AADC is expressed in rat glial cells.

Intramolecular oscillation of the phosphorylation domain of rat cardiac sarcoplasmic reticulum titrated with arachidonoyl phosphatidylcholine

Sarcoplasmic reticulum vesicles were prepared from rat myocardium. The intramolecular oscillation of the phosphorylation domain of Ca(2+)-ATPase in control vesicles and in vesicles titrated with diarachidonoyl phosphatidylcholine was studied with a nanosecond time-resolved fluorometer. The membrane viscosity of the lipid domain was decreased by the lipid titration. The phosphorylation domain was labeled with a fluorophore, anilinonaphthylmaleimide (ANM). The time course of anisotropy decay of ANM fluorescence reflects the localized oscillation in the protein structure. The half-decay time of the anisotropy was decreased by diarachidonoyl titration from 77 nsec in control vesicles to 66 nsec, suggesting an increase in the intramolecular oscillation. Concomitantly observed decreases in membrane viscosity and Ca(2+)-ATPase activity suggest that the decreased membrane viscosity destabilized the Ca(2+)-ATPase protein structure causing a reduction in Ca(2+)-ATPase activity.

[Effects of phospholipid layer on the dynamic microstructure of phosphorylation domain of Ca(2+)-ATPase from sarcoplasmic reticulum prepared from rabbit skeletal muscle]

The effects of phospholipids bilayers imposed on the intramolecular dynamic microstructure of Ca(2+)-ATPase from rabbit skeletal muscle sarcoplasmic reticulum were studied with a nanosecond time-resolved fluorometer. Ca(2+)-ATPase was purified and reconstituted into vesicle membranes. The phosphorylation domain of Ca(2+)-ATPase was labeled with a fluorophore, N-(1-anilinonaphthyl-4) maleimide (ANM). The phospholipids surrounding the hydrophobic segment of Ca(2+)-ATPase were exchanged with phosphatidylcholines of shorter acyl chain length by lipid titration. The membrane viscosity was measured by fluorometry using 1, 6-diphenyl-1, 3, 5-hexatriene (DPH). The membrane viscosity decreased when the intrinsic phospholipids were titrated with phosphatidylcholine having shorter acyl chains, and accompanied with a concurrent decrease in Ca(2+)-ATPase activity. The replacement of native lipids caused an increase in the fluorescence wavelength of ANM-labeled Ca(2+)-ATPase vesicles (red shift). This result suggests a conformational change in which the phosphorylation domain becomes more hydrophilic. The anisotropy decay time was was analyzed as two components, the slower being attributed to the intramolecular oscillation of the phosphorylation domain. The half-decay time of ANM fluorescence anisotropy was 72 +/- 4 nsec in the control vesicles, 69 +/- 3 nsec in di (18: 1) PC, 61 +/- 4 nsec in di (16: 1) PC, 54 +/- 3 nsec in di (14: 1) PC, and 49 +/- 2 nsec in di (12: 0) PC-titrated vesicles. This result suggests that the submolecular oscillation of the phosphorylation domain of Ca(2+)-ATPase is limited by the physical properties of boundary phospholipids, and that changes in the phospholipids cause alterations in the molecular motion of this domain, destabilize Ca(2+)-ATPase and reduce its activity.

Regulation of aromatic L-amino acid decarboxylase by dopamine receptors in the rat brain

Decarboxylation of phenylalanine by aromatic L-amino acid decarboxylase (AADC) is the rate-limiting step in the synthesis of 2-phenylethylamine (PE), a putative modulator of dopamine transmission. Because neuroleptics increase the rate of accumulation of striatal PE, these studies were performed to determine whether this effect may be mediated by a change in AADC activity. Administration of the D1 antagonist SCH 23390 at doses of 0.01-1 mg/kg significantly increased rat striatal AADC activity in an in vitro assay (by 16-33%). Pimozide, a D2-receptor antagonist, when given at doses of 0.01-3 mg/kg, also increased AADC activity in the rat striatum (by 25-41%). In addition, pimozide at doses of 0.3 and 1 mg/kg increased AADC activity in the nucleus accumbens (by 33% and 45%) and at doses of 0.1, 0.3, and 1 mg/kg increased AADC activity in the olfactory tubercles (by 23%, 30%, and 28%, respectively). Analysis of the enzyme kinetics indicated that the Vmax increased with little change in the Km with L-3,4-dihydroxyphenylalanine as substrate. The AADC activity in the striatum showed a time-dependent response after the administration of SCH 23390 and pimozide: the activity was increased within 30 min and the increases lasted 2-4 h. Inhibition of protein synthesis by cycloheximide (10 mg/kg, 0.5 h) had no effect on the striatal AADC activity or on the increases in striatal AADC activity produced by pimozide or SCH 23390. The results indicate that the increases in AADC activity induced by dopamine-receptor blockers are not due to de novo synthesis of the enzyme.(ABSTRACT TRUNCATED AT 250 WORDS)

Estimation of the oxygen gradient across phospholipid bilayers of mitochondria from reperfused rabbit hearts after ischemia

Mitochondria isolated from myocardium exposed to 30 minute ischemia followed by 30 minute reperfusion showed an increase in membrane viscosity and a decrease in wobbling angle of phospholipids, compared with those from the normally perfused myocardium in anesthetized open-chest rabbits. The values for the membrane viscosity were used to estimate the oxygen gradient across the lipid bilayers of mitochondrial membranes with a model of cylindrical diffusion. The effective diffusion coefficient for oxygen, DO2, was approximated to be 6.5 and 6.3 x 10(-5) cm2/sec in the control and ischemic-reperfused area, respectively, by comparing reported DO2 values with values for membrane viscosity. For the surface area of the inner mitochondrial membrane including cristae and for the oxygen consumption rate of the myocardium, reported values for rats and cats, respectively, were employed. Using these values, oxygen gradients across the lipid bilayers of mitochondrial lipid membranes were estimated to be only 0.055 and 0.057 nM in the control and 30 minute ischemic-reperfused myocardium, respectively. If the mitochondrial membranes are hydrated because of the ischemia-reperfusion, the absorption coefficient of the membrane to oxygen will decrease and the oxygen gradient will be increased. In the present study, however, the fluorescence life time of DPH, the hydrophobic fluorophore, showed no shortening despite the ischemia-reperfusion. Hence, no indication of membrane hydration was obtained.

Inhibition of monoamine oxidase-B by (-)-deprenyl potentiates neuronal responses to dopamine agonists but does not inhibit dopamine catabolism in the rat striatum

This report describes experiments designed to determine whether (-)-deprenyl potentiates dopaminergic transmission and whether its mechanism involves the inhibition of dopamine catabolism. Intraperitoneal administration of (-)-deprenyl (0.5-8 mg kg-1) produced a dose-dependent inhibition of striatal monoamine oxidase type B activity whereas monamine oxidase type A activity in the striatum was inhibited only by 8 mg kg-1 of (-)-deprenyl. Intraperitoneal administration of (-)-deprenyl (0.5-4 mg kg-1) did not alter the striatal concentrations of dopamine (DA), 3,4-dihydroxyphenylacetic acid (DOPAC) or homovanillic acid. DOPAC concentrations were decreased by 8 mg kg-1 of (-)-deprenyl. In contrast, administration of clorgyline (2 mg kg-1), a monoamine oxidase type A inhibitor, increased the striatal concentrations of DA and decreased the striatal concentrations of DOPAC and homovanillic acid. The striatal concentrations of 2-phenylethylamine (PE), a putative modulator of striatal DA transmission, were increased by (-)-deprenyl (1-8 mg kg-1) but were unaffected by clorgyline (2 mg kg-1). In electrophysiological studies, single caudate neuron responses to iontophoretically applied (-)-apomorphine and (+/-)-2-(N-phenethyl-N-propyl) amino-5-hydroxytetralin were potentiated by intracarotid injections of PE (30 micrograms kg-1) and i.p. injections of (-)-deprenyl (2 mg kg-1). Both PE and (-)-deprenyl reduced the IT50 of responses to apomorphine and (+/-)-2-(N-phenethyl-N-propyl)amino-5-hydroxytetralin.(ABSTRACT TRUNCATED AT 250 WORDS)

Dynamic microstructure of mitochondrial membranes from rabbit heart subjected to reperfusion after ischemia

The effects of ischemia combined with reperfusion on the dynamic microstructure of mitochondrial membranes were studied in the hearts of anesthetized open-chest rabbits by means of time-resolved fluorometry. The fluorescence of diphenyl hexatriene (DPH) and its anisotropic decay were used to calculate membrane viscosity, wobbling angle of phospholipids and fluorescence life time. The anterior descending branch of the coronary artery was occluded for 15 min and reperfused for 15 min. Mitochondria from the area of the left ventricular wall exposed to ischemia-reperfusion and from an unexposed control area were separately isolated in 8 rabbits. For comparison, mitochondria from ventricular wall exposed to ischemia but not to reperfusion were obtained from 5 rabbits. The membrane viscosity increased from 0.44 to 0.49 poise and the wobbling angle of phospholipids tended to decrease from 59 to 56 degrees at 37 degrees C. The amount of peroxidized lipid rose from 1.5 to 4.3 nmol/mg-protein as expressed with MDA in the mitochondria exposed to ischemia-reperfusion. The fluorescence life time of DPH was slightly longer in the latter than in mitochondria from the control area. None of these parameters was altered in mitochondria exposed only to ischemia. The increase in viscosity observed in mitochondria from the ischemic-reperfused area probably produces a decrease in the diffusion of molecules through mitochondrial membranes. The concurrent tendency of the decrease in wobbling angle of membrane phospholipids suggests a decrease in the size of molecules which can permeate membranes. Limitations in diffusion will affect the metabolic activity of mitochondria and finally, overall cardiac function.