Regulation of recombinant gamma-aminobutyric acid (GABA)(A) and GABA(C) receptors by protein kinase C

Activation of protein kinase C (PKC) by phorbol 12-myristate 13-acetate induced a continuous decrease in the gamma-aminobutyric acid (GABA)-activated current amplitude from recombinant GABA receptors (formed by rho1 or alphabetagamma subunits) expressed in Xenopus oocytes. This decline was due to internalization of receptors from the plasma membrane as confirmed by a decrease in surface fluorescence with green fluorescence protein-tagged receptors as well as a concomitant decrease in surface [(3)H]GABA binding. PMA specifically caused internalization of GABA receptors, but not neuronal acetylcholine receptors (alpha(7) or alpha(4)beta(2)), indicating the internalization was not a general, nonspecific phenomenon. Mutation of rho1 PKC phosphorylation sites, identified by in vitro phosphorylation, did not prevent GABA receptor internalization, nor did coexpression of the rho1 M3-M4 intracellular loop along with rho1 GABA receptors. It is likely that PKC-mediated phosphorylation of other proteins, rather than rho1 itself, was required for the internalization. Both rho1 and alphabetagamma receptors did not degrade after phorbol 12-myristate 13-acetate-induced internalization, but returned to the membrane surface within 24 h. These data suggest internalized receptors can exist in an intracellular compartment that can be delivered back to the plasma membrane. Thus, by regulating GABA receptor surface expression, PKC may play a key role in the regulation of GABA-mediated inhibition.

[Effects of LMP-1 expression on neoplastic cell proliferation and apoptosis in nasopharyngeal carcinoma]

OBJECTIVE

To investigate the effects of LMP-1 expression on neoplastic cell proliferation and apoptosis in untreated nasopharyngeal carcinoma (NPC).

METHODS

Biopsies from 55 untreated NPC cases were collected. EBERs was detected by in situ hybridization. PCNA, LMP-1 and bcl-2 were detected by immunohistochemistry method. Cell apoptosis was demonstrated by TUNEL (TdT-mediated dUTP-x nick end labeling) kit.

RESULTS

(1) The positive LMP-(1) expression rate was 27/55 (49.1%). The median PI (PCNA Index) of LMP-1 positive cases (90.0%) was higher than that of LMP-1 negative cases (80.0%) and the p value was less than 0.05 by rank sum (rs) test. (2) The median TI (TUNEL Index) of LMP-1 positive cases (16.2 per high power field) was also higher than that of LMP-1 negative cases (10.4 per high power field) and the p value was less than 0.05 by rs test. (3) As for the bcl-2 expression percentages, no correlation was found between LMP-1 positive and negative cases. (4) A positive rank correlation existed between PI and TI (rs = 0.368 1, P < 0.01), but no correlation was found between TI and bcl-2 expression percentage.

CONCLUSIONS

(1) NPC with LMP-1 expression have higher levels of PI, maybe resulting from the promotional effect of LMP-1 on cell proliferation. (2) NPC with LMP-1 expression also have a higher level of TI, indicating that LMP-1 can induce cell apoptosis, which could not be blocked by bcl-2 expression. The authors suggest that LMP-1 expression may exert a dual action on neoplastic cell proliferation and apoptosis in untreated nasopharyngeal carcinoma.

Epstein-Barr virus infection in nasopharyngeal lymphoid hyperplasia

OBJECTIVE

To detect whether Epstein-Barr virus (EBV) harbors in nasopharyngeal lymphoid hyperplasia (NPLH) which is frequently to be seen in Guangzhou, a high-incidence area of nasopharyngeal carcinoma (NPC), and to explore the relation between NPLH and development of NPC.

METHODS

Twenty-four 10% formalin-fixed, paraffin-embedded biopsies oef patients with NPLH and elevated serum IgA antibody titer (> or = 1:20) against viral capsid antigen of EB virus (IgA/VCA) were collected from the archives of the Department of Pathology, Sun Yat-sen University of Medical Sciences during the period of January to June, 1993. PCR plus Southern blotting hybridization for detection of EBV DNA W-fragment and in situ hybridization for detection of EB virus encoded small RNAs (EBERs) were performed. All the patients were followed up more than 5 years.

RESULTS

Twenty-two of 24 (91.7%) NPLH tissues contained EBV DNA. A few definitely EBERs positive B-lymphocytes could be found in 17 out of 24 specimens (70.8%). Neither NPC nor any EBV-associated malignancies were developed in all of these 24 patients up to date.

CONCLUSION

Most of the NPLH tissues taken from the patients with an elevated serum IgA/VCA titer carry EBV, which is harbouring in the nuclei of a few infiltrating and hyperplastic B-lymphocytes. The NPLH without epithelial dysplasia can not be recognized as a precancerous lesion, and EBV infection in these lesions is not an important event, having no substantial significance in development of NPC.

Ethanol diet increases the sensitivity of rats to pancreatitis induced by cholecystokinin octapeptide

BACKGROUND & AIMS

Although alcoholism is a major cause of pancreatitis, the pathogenesis of this disorder remains obscure. Failure to produce experimental alcoholic pancreatitis suggests that ethanol may only increase predisposition to pancreatitis. This study sought to develop a model of ethanol pancreatitis by determining if an ethanol diet sensitizes rats to pancreatitis caused by cholecystokinin octapeptide (CCK-8).

METHODS

Rats were fed intragastrically either control or ethanol diet for 2 or 6 weeks. The animals were then infused for 6 hours with either saline or CCK-8 at a dose of 3000 pmol. kg(-1). h(-1), which by itself did not induce pancreatitis. The following parameters were measured: serum amylase and lipase levels, pancreatic weight, inflammatory infiltration, number of apoptotic acinar cells, pancreatic messenger RNA (mRNA) expression of cytokines and chemokines, and nuclear factor (NF)-kappaB activity.

RESULTS

All measures of pancreatitis, as well as NF-kappaB activity and mRNA expression for tumor necrosis factor alpha, interleukin 6, monocyte chemotactic protein 1, macrophage inflammatory protein 2, and inducible nitric oxide synthase, were significantly increased only in rats treated with ethanol plus CCK-8.

CONCLUSIONS

An ethanol diet sensitizes rats to pancreatitis caused by CCK-8. The combined action of ethanol and CCK-8 results in NF-kappaB activation and up-regulation of proinflammatory cytokines and chemokines in the pancreas. These mechanisms may contribute to the development of alcoholic pancreatitis.

COOH-terminally extended secretins are potent stimulants of pancreatic secretion

Posttranslational processing of preprosecretin generates several COOH-terminally extended forms of secretin and alpha-carboxyl amidated secretin. We used synthetic canine secretin analogs with COOH-terminal -amide, -Gly, or -Gly-Lys-Arg to examine the effects of COOH-terminal extensions of secretin on bioactivity and detection in RIA. Synthetic products were purified by reverse-phase and ion-exchange HPLC and characterized by reverse-phase isocratic HPLC and amino acid, sequence, and mass spectral analyses. Secretin and secretin-Gly were noted to coelute during reverse-phase HPLC. In RIA using eight different antisera raised against amidated secretin, COOH-terminally extended secretins had little or no cross-reactivity. Bioactivity was assessed by measuring pancreatic responses in anesthetized rats. Amidated canine and porcine secretins were equipotent. Secretin-Gly and secretin-Gly-Lys-Arg had potencies of 81 +/- 9% (P > 0.05) and 176 +/- 13% (P < 0.01), respectively, compared with amidated secretin, and the response to secretin-Gly-Lys-Arg lasted significantly longer. These data demonstrate that 1) amidated secretin and secretin-Gly are not separable under some chromatographic conditions, 2) current RIA may not detect bioactive COOH-terminally extended forms of secretin in tissue extracts or blood, and 3) the secretin receptor mediating stimulation of pancreatic secretion recognizes both amidated and COOH-terminally extended secretins.

[Detection of Epstein-Barr virus, cell proliferation and apoptosis in thymic tumors]

OBJECTIVE

To investigate the incidence of thymic tumors in Guangzhou, its association with EBV infection and the cell proliferation and apoptosis characteristics of these tumors.

METHODS

EBV encoded small RNAs (EBERs) were detected in 43 thymic tumors and 7 thymic hyperplasia samples by use of in situ hybridization, EBNA-1, LMP-1, PCNA, bcl-2 and p53 were examined using immunohistochemical methods, cell apoptosis was evaluated by TUNEL (TdT-mediated dUTP-X nick end labelling) in situ cell death detection kit.

RESULTS

1. Thymic diseases only accounted for 0.057% of biopsies in the Guangzhou area. Thymic tumor and hyperplasia accounted for 74.7% and 18.6% in thymic diseases respectively. Thymic lymphoepithelimoa-like carcinoma (LELC) occurred in 2.7% of thymic tumors. 2. EBV encoded products (EBERs, EBNA-1 and LMP-1) were not detected in 50 thymic disease specimens. 3. Marked proliferation (3+-4+) grade thymomas (0/18 cases) was much lower than that of thymic carcinomas (10/20 cases), and the marked apoptotic (2+-4+) grade was higher in thymomas (15/18) than the thymic carcinomas (13/20). 4. The p53 protein accumulation rate in thymic carcinomas (8/20) was significantly higher than that of thymomas (1/18). The apoptotic grade is significantly related to p53 accumulation in thymic epithelial tumors. 5. The bcl-2 over expression could be detected both in thymomas and thymic carcinomas.

CONCLUSIONS

1. Thymic diseases, including thymic LELC, is very rare in Guangzhou and is not closely associated with EBV infection. 2. Thymic carcinomas have a relatively rapid growth rate compared to thymomas. 3. p53 gene mutation may play an important role in the carcinogenesis of thymic carcinoma, and bcl-2 over-expression may also be involved in the evolution of thymic epithelial tumors. 4. Wild type p53 protein may exert an apoptosis-inducing function in thymic epithelial tumors, including thymomas and carcinomas, and a proliferation inhibiting function only in thymomas.

Typhoon hazards in the Shanghai area

There are three major typhoon hazards that apply to the Shanghai area. First, galeforce winds can damage buildings and service facilities. The most severe damage from this occurs only when a typhoon strikes Shanghai directly. Second, both the urban and rural sections of Shanghai are liable to flooding during typhoon seasons. These floods occur when typhoon-induced storm surges coincide with high spring tides and meet with high discharges from the river network as a result of the typhoon downpours. Third, typhoon-induced torrential rain has caused waterlog hazards, particularly in the most densely populated parts of Shanghai. The waterlog hazard has been exacerbated by land subsidence and poor management of pumping systems. In order to prevent disasters happening and reduce the scale of damage, the government has issued construction guidelines and invested in flood defences. Further measures are to be brought in including engineering projects, educational programmes and insurance policies.

Development of a Bolometer Detector System for the NIST High Accuracy Infrared Spectrophotometer

A bolometer detector system was developed for the high accuracy infrared spectrophotometer at the National Institute of Standards and Technology to provide maximum sensitivity, spatial uniformity, and linearity of response covering the entire infrared spectral range. The spatial response variation was measured to be within 0.1 %. The linearity of the detector output was measured over three decades of input power. After applying a simple correction procedure, the detector output was found to deviate less than 0.2 % from linear behavior over this range. The noise equivalent power (NEP) of the bolometer system was 6 × 10-12 [Formula: see text] at the frequency of 80 Hz. The detector output 3 dB roll-off frequency was 200 Hz. The detector output was stable to within ± 0.05 % over a 15 min period. These results demonstrate that the bolometer detector system will serve as an excellent detector for the high accuracy infrared spectrophotometer.

[Effect of excitatoxicity on Ca2+/CaM PK II activity in rat hippocampal slices]

The relation between Ca2+/CaM PK II activity and excitatoxicity was studied in an in vitro model of rat hippocampal slices. The slices were exposed to 50-200 mumol.L-1 glutamate or 25-100 mumol.L-1 NMDA and glucose-free Krebs buffer for 30 min after being recovered to normal conditions by 2 hours of incubation with standard Krebs buffer. The results showed that inhibition of Ca2+/CaM PK II activity in rat hippocampal slices was induced by exogenous EAA (glutamate or NMDA), and Ca2+/CaM PK II activity values decreased to 50.1% and 44.7% of control at 200 mumol.L-1 glutamate and 100 mumol.L-1 NMDA, respectively; MK801, but not DNQX, antagonized EAA-induced inhibition of Ca2+/CaM PK II activity. When the slices were pretreated with MK801 prior to exposure to 200 mumol.L-1 glutamate or 100 mumol.L-1 NMDA, the Ca2+/Cam PK II activity values were 91.5% and 96.7%, respectively. The changes of extracellular Ca2+ or Mg2+ concentration influenced Ca2+/CaM PK II activity of the slices exposed to exogenous glutamate; Ca2+/CaM PK II activity values in the presence of extracellular Ca2+ was lower than that in the absence of extracellular Ca2+, and it changed from 50.1% of control (presence of Ca2+) to 64% of control (absence of Ca2+) at 200 mumol.L-1 glutamate, but Ca2+/CaM PK II activity values in the presence of extracellular Mg2+ was higher than that in the absence of extracellular Mg2+, and it changed from 50.1% of control(presence of Mg2+) to 36.6% of control (absence of Mg2+) at 200 mumol.L-1 glutamate. The results suggest that NMDA receptor may be involved in excitotoxicity-induced inhibition of Ca2+/CaM PK II activity.

High-Quality Brewster's Angle Polarizer for Broadband Infrared Application

We have designed and constructed a linear polarizer for use with visible and infrared radiation. The broadband polarizer consists of four germanium plates arranged in a chevron geometry. Input radiation is incident near Brewster's angle for the first plate such that the reflected beam is preferentially s-wave polarized. This reflected beam is steered subsequently to the successive plates, always intersecting near Brewster's angle. The beam polarization at the output of the device is almost completely s-wave polarized. The ratio of the paraxial flux of the nearly extinguished p-wave polarized light to the s-wave polarized light transmitted through the device is found to be less than 10(-5) for laser illumination at wavelengths of 0.633, 1.32, 3.39, and 10.6 mum. Calculations predict that extinction ratios less than 10(-5) are achievable over the wavelength range from 0.4 mum to beyond 500 mum. Alternative design geometries involving fewer plates are also described along with their advantages and disadvantages.

The effect of neferine on foam cell formation by anti-low density lipoprotein oxidation

Oxidatively modified low density lipoprtein (LDL) plays an important role in atheroslerosis (AS) development. To investigate the role of neferine (Nef) in anti-LDL oxidation and foam cell formation, the lipoprotein was derived and subjected to three different treatments: N-LDL (normal LDL), Cu2+ + LDL and Cu2+ + Nef + LDL. The LDLs were put at 25 degrees C for 24 h and the thiobarbituric acid reactive substance (TBARS) values were determined. They were 0.57 +/- 0.2, 6.01 +/- 0.22 and 2.26 +/- 0.13 nmol/mg protein, respectively. The difference was very significant (P < 0.01) for each two groups by t test. Mouse peritoneal macrophage (M phi) were exposed to 50 micrograms protein/ml of Cu2+ + LDL and Cu2+ + Nef + LDL at 37 degrees C for 60 h. The tryglyceride (TG) and total cholesterol (TC) content in M phi were assayed. The results showed that Cu2+ + LDL was more efficient than Cu2+ + Nef + LDL in stimulating lipid accumulation in M phi (P < 0.001). The study demonstrated that Nef could inhibit Cu(2+)-mediated LDL oxidation and thereby inhibiting macrophage-derived foam cell formation.

[Association of epstein-barr virus with lymphoepithelioma-like carcinoma of the lung]

OBJECTIVE

To study the relationship between pulmonary lymphoepithelima-like carcinoma (LELC) and Epstein-Barr virus (EBV).

METHODS

30 cases of LELC and 19 cases of non LELC pulmonary pulmonary specimens were studied by in situ hybridization and immunohistochemistry techniques to detect EB virus small RNA (EBERs), latent menbrane protein-1 (LMP-1) and virus capsid antigen (VCA).

RESULTS

The detection rates for EBER, LMP-1 and VCA were 93.3% (28/30), 53.3% (16/30) and 23.3% (7/30) respectively. LMP-1 positive carcinoma cells were not found in the 19 non-LELC specimens, which were used as the controls.

CONCLUSION

Pulmonary LELC is closely associated with latent EBV infection and may be an important factor involved in the development and progression of LELC. In addition, EBV lytic gene products may sometimes be found in a small portion of LELC cells.

[Studies on the mechanism of protection of cultured neurous by ketamine anoxia/reoxygenation-induced injury]

The effects of anoxia/reoxygenation (A/R) and glutamate on cultured cortical neurons from 16 to 18-day-old fetal rats and the protective effect of ketamine were studied. The 12-day cultures of 12 days were exposed to anoxia (5 h) followed by reoxygenation (0-24 h). Following progressive A/R, the release of lactate dehydrogenase (LDH) into the bathing medium obviously increased and exogenous glutamate (3 h) also markedly increased the release of LDH. When the cultures were pretreated with ketamine before A/R, the amounts of LDH efflux in culture medium were significantly less than those of controls. These results demonstrate that the cultured cortical neurons are seriously damaged by A/R and exogenous glutamate. Such damage could be attenuated by ketamine, suggesting that the neurotoxic effect of glutamate and NMDA (N-methyl-D-aspartate) receptors play an important role in the process of ischemia-induced damage in the brain.

Regulation of ApoE gene expression in mouse peritoneal macrophages by VLDL

Mouse peritoneal macrophages (MPM) were incubated with ApoE-poor VLDL or ApoE-rich VLDL at same concentrations for 24 h. The ApoE mRNA content increased in both groups than that in control and the highest ApoE mRNA content was seen in MPM incubated with ApoE-poor VLDL. The results suggest that VLDL could stimulate ApoE gene expression in MPM and the ApoE-poor VLDL has more pronounced effect. We think that the ApoE secreted by MPM may be incorporated into VLDL, especially the ApoE-poor VLDL, and thereby enhance the uptake of those lipoproteins by MPM or other local cells via ApoE-mediated receptor pathways.