[Study on the mechanism of early pancreatic exocrine function changes in severely scalded rats]

Objective: To explore the mechanism of early pancreatic exocrine function changes in severely scalded rats. Methods: The experimental research methods was used. Eighty male Sprague-Dawley rats aged 7-8 weeks were divided into simple sham injury group (n=8), sham injury+cholecystokinin octapeptide (CCK8) group (n=8), severe scald+CCK8 group (n=32), and extremely severe scald+CCK8 group (n=32) by the random number table, which were treated accordingly. Immediately after injury of rats in the 2 sham injury groups and 1, 2, 3, and 7 days after injury of rats in the 2 scald groups, the improved methods including pancreatic duct puncture and catheterization were used to dynamically collect the pancreatic-bile juice (PBJ) of rats. The PBJ secretory volume within 1 h was recorded, and the content of pancreatic lipase, α-amylase, and trypsin in PBJ was detected by enzyme-linked immunosorbent assay (ELISA), and the number of samples was 8. The femoral venous blood was collected, and the concentrations of pancreatic lipase and α-amylase in serum were detected by standard colorimetry to reflect their activity (n=8). The pancreatic tissue was extracted, and the levels of interleukin-1β (IL-1β) and IL-6 in pancreatic tissue were detected by ELISA (n=8), the expression of hypoxia-inducible factor 1α (HIF-1α) in pancreatic tissue was detected by immunofluorescence method, and the histopathological changes in pancreatic tissue were observed by hematoxylin-eosin staining, the severity of pancreatic tissue injury in the 2 scald groups was evaluated by modified Schmidt method (n=6), and the ultrastructure of acinar cells in pancreatic tissue was observed by transmission electron microscopy. Data were statistically analyzed with analysis of variance for factorial design, Tukey test, independent sample t test, and least significant difference test. Results: Compared with the PBJ secretory volume (0.740±0.030) mL in the pancreatic tissue of rats in simple sham injury group within 1 h immediately after injury, the (0.823±0.033) mL in sham injury+CCK8 group was significantly increased (t=4.92, P<0.05). Compared with that of rats in sham injury+CCK8 group immediately after injury, the PBJ secretory volume of rats within 1 h in severe scald+CCK8 group ((0.681±0.024), (0.608±0.056), (0.525±0.025), and (0.720±0.044) mL) and extremely severe scald+CCK8 group ((0.540±0.025), (0.406±0.021), (0.475±0.036), and (0.690±0.018) mL) was significantly decreased on 1, 2, 3, and 7 days after injury (P<0.05). Compared with that in severe scald+CCK8 group, the PBJ secretory volume of rats within 1 h in extremely severe scald+CCK8 group was significantly decreased on 1 and 2 days after injury (P<0.05). Compared with that of rats in simple sham injury group immediately after injury, the content of pancreatic lipase, α-amylase, and trypsin in PBJ of rats in sham injury+CCK8 group immediately after injury was significantly increased (with t values of 4.56, 3.30, and 4.99, respectively, P<0.05). Compared with that of rats in sham injury+CCK8 group immediately after injury, the content of pancreatic lipase and α-amylase in PBJ of rats in severe scald+CCK8 group and extremely severe scald+CCK8 group was significantly decreased on 1, 2, 3, and 7 days after injury (P<0.05), the trypsin content in PBJ of rats in extremely severe scald+CCK8 group was significantly decreased on 2 days after injury (P<0.05). Compared with that in severe scald+CCK8 group, the content of pancreatic lipase in PBJ of rats in extremely severe scald+CCK8 group was significantly decreased on 1, 2, and 3 days after injury (P<0.05), and the content of α-amylase and trypsin in PBJ was significantly decreased on 1 and 2 days after injury (P<0.05). There were no statistically significant differences in the activities of pancreatic lipase and α-amylase in serum of rats among the 4 groups at various time points after injury (P>0.05). Compared with that of rats in sham injury+CCK8 group immediately after injury, the levels of IL-1β in pancreatic tissue of rats in severe scald+CCK8 group on 1, 2, and 3 days after injury and in extremely severe scald+CCK8 group on 1, 2, 3, and 7 days after injury were significantly increased (P<0.05), and the levels of IL-6 in pancreatic tissue of rats in severe scald+CCK8 group and extremely severe scald+CCK8 group were significantly increased on 1, 2, 3, and 7 days after injury (P<0.05). Compared with that in severe scald+CCK8 group, the IL-1β level in pancreatic tissue of rats in extremely severe scald+CCK8 group was significantly increased on 2 and 3 days after injury (P<0.05), and IL-6 level in pancreatic tissue was significantly increased on 2 days after injury (P<0.05). The expression levels of HIF-1α in pancreatic tissue of rats in simple sham injury group and sham injury+CCK8 group immediately after injury were lower; and compared with that in sham injury+CCK8 group immediately after injury, the expression levels of HIF-1α in pancreatic tissue of rats in the 2 scald groups increased to a certain extent at different time points after injury, and the expression position was transited from the edge of the pancreatic tissue to the whole pancreas, the expression levels of HIF-1α in pancreatic tissue of rats in the 2 scald groups tended to be normal on 7 days after injury. Compared with that in simple sham injury group immediately after injury, the proportion of acinar cell cytoplasm in pancreatic tissue of rats in sham injury+CCK8 group was increased; and with the increase of time after injury, edema, hemorrhage, necrosis, and inflammatory infiltration appeared in pancreatic tissue of rats in the 2 scald groups. Compared with that in severe scald+CCK8 group, the scores of edema, inflammatory cell infiltration, bleeding, and necrosis in pancreatic tissue of rats in extremely severe scald+CCK8 group were increased to varying degrees at various time points after injury, and the scores of pancreatic tissue of rats in the 2 scald groups basically recovered to normal on 7 days after injury. Compared with that in simple sham injury group immediately after injury, the number of enzyme granules in acinar cells of pancreatic tissue of rats in sham injury+CCK8 group was increased, and with the increase of time after injury, the enzyme granules in acinar cells of rats in the 2 scald groups were gradually reduced basically. Conclusions: The exocrine functions of pancreas, such as synthesis and secretion of pancreatic enzymes, are decreased in the early stage in severely scalded rats. And the greater the scalded area, the more significant the decline of pancreatic exocrine function. This change may be related to hypoxic injury and inflammation in pancreatic tissue after severe scald.

[Study of the inhibitory effect of cell entry inhibitory ezetimibe on hepatitis B virus in vitro]

Objective: To study the inhibitory effect of ezetimibe in an experimental model of human hepatoma cell line (HepaRG) infected with hepatitis B virus (HBV) positive human serum in vitro. Methods: Mature HepaRG cells were divided into a treatment group (received drugs) and a control group (did not receive drugs). In the ezetimibe prevention experiment, the cells in the treatment group was treated with drugs 2 h before infection and 24 h during infection. In the ezetimibe treatment experiment, the cells in the treatment group were treated with drugs for 6 ~ 10 days continuously after 24 hours of HBV infection. The expression of HBV DNA and intracellular cccDNA in the supernatant was detected by fluorescence quantitative PCR. Hepatitis B surface antigen (HBsAg) and hepatitis B e antigen (HBeAg) content in the cell supernatant were detected by chemiluminescence. Analysis of variance was used to compare the differences between multiple groups. Pairwise comparisons among groups were followed by t- test with normal distribution. P < 0.05 was considered as statistically significant. Results: Ezetimibe prevention experiment showed that compared with control group, the treatment group was added with 20, 60, and 100 μmol/L ezetimibe before and during infection, and the HBV DNA content in the supernatant 2 days before was significantly reduced (P < 0.05) in the treatment group. Compared with the control group, the HBsAg expression level 2 days before was significantly reduced (P < 0.05) with the addition of 60 μmol/L ezetimibe in the treatment group. Compared with the control group, the expression level of intracellular cccDNA was significantly reduced (P < 0.05) after 10 days with the addition of 100μmol/L ezetimibe in the treatment group. Ezetimibe treatment experiment showed that cccDNA content in the cells were significantly lowered with the immediate addition of 60μmol/L ezetimibe 24 hours after infection for 10 days when compared to control group (P < 0.05). Conclusion: Ezetimibe, as a cytosolic inhibitor, has a certain inhibitory effect on hepatitis B virus infection in both prevention and treatment experiment.

TrxR1 to promote adriamycin resistance in MCF-7 breast cancer cells by upregulating both gene expression level and enzyme activity: Reversed by shikonin

e15070

Background: Adriamycin is one of the effective drugs commonly used in the treatment of advanced breast cancer, but its high incidence of drug resistance and cardiotoxicity limit the application of doxorubicin. Recent evidence shows that increased antioxidant capacity of cancer cells is associated with resistance to chemotherapy. Shikonin, a derivative of Lithospermum erythrorhizon Sieb.et Zucc, displays broad antitumor activity and direct cytotoxicity on various tumor cells. Our previous study shows that shikonin was enabled to directly binding and inhibiting TrxR1, which significantly downregulates intracellular ROS in cancer cells, suggesting that shikonin might be a promising drug candidate. In this study, we identified the relationship between TrxR1 and chemotherapeutic drug resistance in cancer cells and effects of shikonin with and without adriamycin on adriamycin-resistance cells. Methods: The direct DTNB reduction assay was employed to test the enzyme activity of TrxR1. Cultured ADR-resistant MCF-7 cells were assayed for their half maximal inhibitory concentration (IC50) values and apoptosis using an CCK8 assay and Annexin V-FITC/PI-labeled flow cytometry. Drug resistance was evaluated by inhibitory concentration (IC50) values and immunoblotting multidrug resistance protein 1 (MDR1) and breast cancer resistance protein (BCRP). TrxR1 knockdown was silenced by siRNA, leading to reducing the IC50 value of ADR-resistant MCF-7 cells. Dysfunctional endoplasmic reticulum was measured by western blot analysis of endoplasmic reticulum (ER) stress signaling pathways and observation of morphology using a transmission electron microscope. Results: We found that the TrxR1 was significantly enhanced in adriamycin-resistant (ADR/MCF7) cells.Furthermore, the decreased TrxR1 function by TrxR1-knockdown or TrxR1 inhibitor piperlongumine increased MCF-7 cells sensitivity to adriamycin. Treatment of ADR/MCF7 cells with shikonin (2.5,5,10,20,40 μM) dose-dependently inhibited TrxR1 enzyme activity and the clearance of dysfunctional endoplasmic reticulum, and induced cell apoptosis. Conclusions: Our results suggest that TrxR1 is critical for adriamycin resistance in breast cancer cells(ADR/MCF7),and shikonin or other inhibitors of TrxR1 would be potential in the treatment of cancer cells with adriamycin resistance.

[Relationship between parasitic infections and hygiene hypothesis: a review]

Recently, the incidence of infectious diseases continues to decline in many developed countries; however, the incidence of autoimmune diseases and allergic asthma appears a tendency towards a rise over years. "Hygiene hypothesis" provides new insights into the treatment of autoimmune disorders and allergic diseases based on parasitic infections. Increasing evidence shows that parasitic infections may effectively inhibit the development of diabetes, multiple sclerosis, inflammatory bowel disease, rheumatoid arthritis and allergic asthma. There are complex mechanisms underlying the relationship between parasitic infections and "hygiene hypothesis", among which regulatory T (Treg) cells and Th17 cells are becoming a hot topic of research. This paper reviews the progresses in the research on the relationship between parasitic infections and "hygiene hypothesis", and summarizes the roles of Treg cells and Th17 cells in the interplay between parasitic infections and "hygiene hypothesis".

[Feasibility and safety of paclitaxel-eluting balloon for the treatment of de novo coronary lesions]

Objective: To evaluate the safety and feasibility of treating de novo coronary lesions with paclitaxel-eluting balloon. Methods: This is a retrospective study, which enrolled 76 patients with 80 de novo coronary lesions treated with paclitaxel-eluting balloons(<30% residual stenosis and there was no blood flow limited dissection after pretreatment) from April 2015 to November 2016 in Guangdong general hospital. The data of basic characteristics,procedures,devices and follow-up information were retrieved and analyzed. The primary endpoint was the composite of cardiac death, recurrent myocardial infarction and target lesion revascularization. Results: (1)The age was (63.3±10.3) years. There were 68.4%(52/76) acute coronary syndrome patients, prevalence of type 2 diabetes was 36.8%(28/76), and 64.5%(49/76)patients with at least one high bleeding risk. (2)The lesion length was (17.4±7.6)mm, and the stenosis was (88.1±8.2)%.The reference vessel diameter≥2.75 mm accounted for 51.2% (41/80), and bifurcation stenosis accounted for 67.5%(54/80). (3)53.7%(43/80) lesions were pretreated with scoring balloon to optimize plaque modification. The paclitaxel-eluting balloon length and diameter were (22.3±5.5)mm and (2.74±0.52)mm.The residual stenosis was (12.3±10.3)%. Procedural success was 88.8%(71/80).Bail-out stenting rate was 5.0%(4/80). (4)The median follow-up duration was 12(6, 25) months. Primary endpoint occurred in 3 cases (3.9%), including 2 cardiac deaths(1 patient died of recurrent myocardial infarction, and 1 patient died of acute heart failure induced by severe mitral insufficiency), and one patient receivedtarget lesion revascularization. Conclusion: In case of no more than 30% residual stenosis and no blood flow limited dissection after lesion pretreatment,it is safe and feasible to treat de novo coronary lesionsusing paclitaxel-eluting balloon.

[Advances in immunotherapy of pancreatic ductal adenocarcinoma]

The morbidity of pancreatic ductal adenocarcinoma (PDAC) has been increasing over years, while the treatment efficacy and prognosis of PDAC remain far from satisfying. The newly-ermerged tumor immunotherapy has not only made lots of breakthroughs in various malignancies, but also brought an opportunity to the treatment of pancreatic cancer.PDAC immunotherapies, mainly including vaccine therapy, adoptive T cell thanfer therapy, checkpoint blockade therapy, have achieved a certain effect, however, the clinical outcomes have not been satisfactory. Therefore, the combination of immunotherapies based on different theoretical views is important and is likely to be the trend in the future. Carcinoma associated fibroblast (CAF) is the most common cell in pancreatic cancer stromal component. It will be helpful to develop more potential therapeutic targets by further exploring CAF and the mechanism of fibrosis mediated immunosuppression.

[Preliminary influence of 2015 cigarette excise tax up-regulation on cigarette retail price]

Objective: To evaluate the impact of cigarette excise tax up-regulation on the retail price of cigarettes in 2015. Methods: Nominal and real price of selected cigarette varieties were calculated with data from Tobacco Retail Price Monitoring Project, which was conducted in 10 cities of China from 2013 to 2015. The trend of the cigarette prices changing was analyzed with annual data. Results: A total of 352 varieties of cigarettes were surveyed during the three years. The nominal price of these cigarettes did not change significantly from 2013 to 2014. Compared with nominal price of 2014, the price of 286 varieties increased and the price of 10 most popular varieties increased from 0.6% to 7.4% after cigarette excise tax increased, but the actual prices had both rise and fall compared with 2013. Conclusions: Cigarette excise tax raise in 2015 had influence on the retail price of cigarettes. But the increase in retail price was very limited, if factors including inflation and purchasing power are taken into consideration. Therefore, the influence of 2015 cigarette excise tax raise on tobacco control needs further evaluation.

[Evaluation of efficacy and safety of pelvic arterial embolization in women with primary postpartum hemorrhage]

OBJECTIVE

To evaluate the efficacy and safety of pelvic arterial embolization (PAE) in women with intractable primary postpartum hemorrhage (PPH).

METHODS

Clinical data of 36 cases were analyzed retrospectively in which women underwent PAE for intractable primary PPH in Peking Union Medical College Hospital between Jan 2006 and Jan 2015. The success rate of PAE were measured and possible predictive risk factors associated with treatment failure were analyzed. The complications secondary to PAE were also recorded.

RESULTS

(1) The etiology of PPH. Among the 36 cases, 21 patients delivered viginally (Group VD) and 15 received cesarean section (Group CS). The most frequent cause of PPH was uterine atony (72%, 26/36). The less common causes were placental problems (28%, 10/36), genital tract trauma (6%, 2/36) and coagulation defects (3%, 1/36) in turn. Three patients (8%, 3/36) had combined causes. (2) Interventions before PAE. Uterotonic medications were used in all patients. 31 patients received carboprost methylate suppositorites, 27 received carbetocin and 31 received carboprost tromethamine. Besides, 20 patients received one or more surgical interventions before PAE. PAE was performed when these interventions failed. (3) Characteristics of PAE. Altogether 78 arteries were embolized in 36 cases. Embolization of bilateral uterine arteries was performed in 31 cases, right internal iliac artery and bilateral inferior epigastric arteries were embolized in one case. Right internal pudendal artery, bilateral uterine arteries and bilateral internal iliac arteries were embolized in one case. And bilateral uterine arteries, bilateral internal iliac arteries were embolized in one case. In the other 2 cases, bilateral internal iliac arteries were embolized. (4) Efficacy of PAE. The overall technical success rate of PAE was 100%(36/36), while the clinical success rate was 94%(34/36). All patients survived. (5) Complications of PAE. 15 patients were transferred to ICU after PAE for 1 to 7 days. Except self-limited fever, no puncture site hematoma, buttock necrosis or vessel rupture was observed. The effect on menstrual cycle and fertility were followed in 25 patients. 17 (68%, 17/25) reported resumption of normal menses and 8 (32%, 8/25) reported amenorrhea. Three pregnancies after PAE were observed.

CONCLUSION

PAE is a safe and effective treatment for intractable primary PPH which can prevent hysterectomy and preserve fertility of patients.

[Study on the pharyngeal constriction and function of cricopharyngeal muscle in normal persons using dynamic magnetic resonance imaging]

OBJECTIVE

To investigate the superiority of dynamic magnetic resonance imaging as an assessment method of pharyngeal constriction and cricopharyngeal muscle function, and introduce a new way to measure the pharyngeal constriction ratio, anteroposterior diameter of esophageal entrance and thickness of cricopharyngeal muscle in healthy volunteers.

METHODS

Twenty volunteers who were assessed as normal by fiberoptic endoscopic evaluation of swallowing and videofluoroscopic swallowing study were included in this study. With the use of 3.0T magnetic resonance imaging, Fiesta sequence and Asset technique, the median sagittal plane and intervertebral transverse plane from C1 to C5 were scanned repeatedly. Pharyngeal constriction ratio in the median sagittal and intervertebral transverse plane, anteroposterior diameter of esophageal entrance and thickness of cricopharyngeal muscle were assessed and the data were analysed by SPSS13.0.

RESULTS

The intervertebral transverse plane between C1 and C2 was superior in observation of pharyngeal constriction ratio in the same way that the plane between C4 and C5 was superior in cricopharyngeal evaluation. The average of sagittal and intervertebral pharyngeal constriction ratio were estimated as 0.08±0.02, 0.09±0.04 respectively and the average of thickness of cricopharyngeal muscle and anteroposterior diameter of esophageal entrance were (6.50±1.69) mm, (1.99±0.76) mm respectively.

CONCLUSION

Dynamic magnetic resonance imaging was superior in assessing the function of pharyngeal constriction and cricopharyngeal muscle by scanning the swallowing process in the median sagittal and intervertebral transverse plane.

Composition and structure of microbial communities associated with different domestic sewage outfalls

The diversity of microbiota in waste waters has not been thoroughly examined, despite the potential impact of microbes on effluent quality. Wastewater microbial communities harbor pathogenic bacteria, viruses, and parasites. To study microbial communities in domestic sewage outfalls, 454 pyrosequencing technology was used to investigate the composition of microbial communities associated with municipal wastewater during different seasons sampled over the course of one year. A total of 195,103 16S rRNA gene sequences were obtained from 20 samples. The R software was used to calculate the number of indices describing the alpha diversity associated with each bacterial assemblage. In this study, the a-diversity index (H', D, J), in which higher numbers represent more diversity, was found to change with seasonal cycle. The diversity of bacterial assemblages was high in all samples, indicating that species diversity was also very high. The taxonomic composition of the assemblages varied considerably among samples, with some dominated by Proteobacteria, while others were dominated by Bacteroidetes or Firmicutes. In 2 samples, the relative prevalence of Proteobacteria exceeded 90%. α-Proteobacteria, b-proteobacteria, and g-proteobacteria represented 90% or more of all Proteobacteria. The present characterization of wastewater from five sewage outfalls indicated the presence of some pathogenic bacteria. The g-Proteobacteria in sewage wastefalls identified in this study included Enterobacteriaceae, Vibrionaceae, Pseudomonadaceae, Salmonella, Yersinia, Vibrio, and Pseudomonas aeruginosa.

Intraarterial thrombolysis and stent placement for acute basilar artery occlusion

PURPOSE

To study retrospectively the prognostic factors for acute basilar artery occlusion treated with intraarterial thrombolysis and stent placement.

MATERIALS AND METHODS

Within 3-48 hours of disease onset, 52 patients with basilar artery occlusion were treated with emergency intraarterial thrombolysis with recombinant tissue plasminogen activator (rtPA) or urokinase (UK) or intraarterial thrombolysis combined with stent placement. Sixteen patients simultaneously received stent placement for the partial recanalization of basilar artery occlusion after intraarterial thrombolysis. The National Institutes of Health Stroke Scale (NIHSS) scores and the modified Rankin Scale (mRS) scores of the patients were estimated.

RESULTS

A favorable clinical outcome occurred in 22 patients (42.3%), and 20 patients (38.5%) died. The survival rate was 61.5% (32 patients). Successful recanalization of basilar artery occlusion was achieved in 24 patients (46.2%), and partial recanalization was achieved in 16 patients (30.7%). The rate of recanalization was 76.9%. NIHSS scores less than 14, treatment time window less than 24 hours, and a good recanalization were markedly correlated with good clinical prognosis. NIHSS scores less than 14 and treatment time window less than 24 hours were significantly correlated with recanalization. NIHSS scores less than 14 and good recanalization could act as independent predictors for clinical prognosis.

CONCLUSIONS

NIHSS scores less than 14 on admission and successful recanalization can predict favorable outcome for patients with basilar artery occlusion. This study shows that intraarterial thrombolysis and stent placement may be a useful treatment for acute basilar artery occlusion.

HLA-G polymorphism in a Chinese Han population with recurrent spontaneous abortion

Reproduction is an important biological phenomenon posing an immunological paradox because the semiallogeneic fetus survives by evading maternal immune recognition. The detailed mechanisms behind this maternal-fetal immunotolerance remain elusive. Human leucocyte antigen (HLA)-G, a non-classical HLA class I antigen, initially identified as a molecule selectively expressed on extravillous cytotrophoblasts and first studied in the context of pregnancy, has long been supposed to play a critical role in fetal-maternal immunotolerance. To investigate the role of HLA-G polymorphism in this process and whether the HLA-G genotype is associated with an increased risk for a subsequent miscarriage, 69 women with three or more recurrent spontaneous abortions (RSA) and 146 fertile control women were genotyped for the HLA-G locus in this study. To our knowledge, this is the first report on HLA-G polymorphism in RSA and in normal fertile women from a Chinese Han population. Nine HLA-G alleles were detected in the fertile control group; however, the allele HLA-G*0103 was absent in the RSA group. No statistical significance was observed in the distribution of HLA-G alleles between the two groups. The frequency of the null allele HLA-G*0105 N in the RSA group and in normal fertile women is 0.7% and 1.4%, respectively. Our data suggested that there was no association of HLA-G polymorphism with RSA.

Modulation by divalent cations of GABA rho 1 receptor from human retina expressed in Xenopus oocytes

OBJECTIVE

To investigate functional homooligomeric GABA rho 1 receptors expressed in Xenopus oocytes and the modulation of divalent cations.

METHODS

GABA rho 1 cDNA from human retina was transcribed in vitro to obtain sense rho 1 mRNA, which was microinjected into Xenopus oocytes. Two-electrodes voltage clamp technique was performed to record GABA-induced currents.

RESULTS

Expressed receptors were found to have similar properties to GABAc receptors characterized in the retina. Cl-currents induced by GABA were blocked by picrotoxin instead of bicuculline. GABA-induced currents reversed at -19 +/- 2.5 mV, and EC50 was 3.3 mumol/L. Zn++ modulated GABA-induced currents with an IC50 = 9.6 mumol/L. Ni++, Cu++ and Cd++ inhibited GABA rho 1 obviously, too. Their rank order of potency was Zn++ > Ni++ > Cu++ > Cd++.

CONCLUSION

Zinc (10 mumol/L) inhibited GABA-induced currents in a competitive manner, and its action was sensitive to extracellular pH. Site-directed mutagenesis revealed that substitution of a single histidine residue (H44 and H48) failed to affect zinc sensitivity.

v-Ha-RaS oncogene upregulates the 92-kDa type IV collagenase (MMP-9) gene by increasing cellular superoxide production and activating NF-kappaB

Matrix metalloproteinase 9 (MMP-9) degrades basement membrane type IV collagen and is expressed during cellular migration and invasion. Here we show that v-Ha-Ras overexpression in rat kidney epithelial cells (REC) caused upregulation of MMP-9 gene expression in part by increasing cellular oxidant levels. v-Ha-Ras mediated the production of superoxide in Ras-transfected cells, which was associated with upregulated MMP-9 gene expression. Conversely, v-Ha-Ras expression decreased steady-state levels of mRNAs from tissue inhibitor of metalloproteinase 1 (TIMP-1), an inhibitor of MMP-9; plasminogen activator inhibitor 1 (PAI-1), which indirectly activates MMP-9 by increasing plasmin levels; and collagen IV, a substrate of MMP-9 and a major component of basement membrane. Gel mobility shift assays demonstrated that Ras overexpression enhanced NF-kappaB, but not AP-1 DNA binding to motifs in the MMP-9 gene promoter. The Ras-induced increase in NF-kappaB DNA binding could be inhibited by treatment with the antioxidants N-acetyl-L-cysteine and glutathione monoester, suggesting that intracellular oxidant levels can mediate MMP-9 transcription. Our findings identify an important role for Ras in the regulation of MMP-9 expression, and suggest that increased superoxide production can upregulate MMP-9 expression and thus contribute to malignant conversion.

V-Ha-Ras overexpression induces superoxide production and alters levels of primary antioxidant enzymes

Reactive oxygen species have been shown to play important roles in v-Ha-Ras mitogenic signaling. We hypothesized that v-Ha-Ras overexpression would induce superoxide production, and therefore modify expression of the primary antioxidant enzyme system. We have demonstrated that immortal rat kidney epithelial cells stably transduced with constitutively active v-Ha-ras produced significantly larger amounts of superoxide radical than wild-type or vector-transfected control cells. The levels of the primary antioxidant enzymes copper- and zinc-containing superoxide dismutase, manganese-containing superoxide dismutase, catalase, and glutathione peroxidase were increased in the superoxide-overproducing cells. DNA-binding activities of the transcription factors activator protein-1, activator protein-2, and nuclear factor-kappaB were all enhanced in the superoxide-overproducing cells. These v-Ha-ras transduced cells also had a shortened cell doubling time and higher plating efficiency, and displayed greater constitutive levels of phosphorylated mitogen-activated protein kinases. These data demonstrate that v-Ha-Ras overexpression increases superoxide production and this apparently affects a wide variety of cell signaling and redox systems.

Protective effect of nimodipine against cerebral injury induced by subacute carbon monoxide intoxication in mice

AIM

To study the effects of nimodipine on delayed cerebral injury in mice from subacute carbon monoxide (CO) exposure.

METHODS

Mice were exposed to CO (100 mL/kg, ip) once a day, continuously for 7 d. After 7-d CO-exposure, mortality in mice, changes in learning ability and memory using passive avoidance test, the pathomorphologic observation of brain tissue slices, and changes of monoamine oxide (MAO)-B activities in cerebral tissue were studied. Nimodipine was administered 30 min before CO-exposure every time.

RESULTS

The preadministration of nimodipine decreased the mortality in mice, almost reversed the impairment of learning and memory function, prevented the hippocampal neurons against delayed death and blunted the rise of MAO-B activity after subacute CO poisoning of mice.

CONCLUSION

Pretreatment with nimodipine markedly prevented mice from delayed encephalopathy after CO poisoning.

Improved version 2.0 qualitative and quantitative AMPLICOR reverse transcription-PCR tests for hepatitis C virus RNA: calibration to international units, enhanced genotype reactivity, and performance characteristics

Version 2.0 qualitative and quantitative AMPLICOR reverse transcription-PCR tests for HCV were designed to improve on the performance of first version of the hepatitis C virus (HCV) tests. The new tests were calibrated in international units, the new commonly accepted standard unit of measurement for HCV RNA. The sensitivity of the qualitative tests was enhanced by modifying the specimen processing procedure to achieve a limit of detection 50 IU/ml. The limit of detection for the quantitative tests was 600 IU/ml. Modifications to the amplification reaction mixture and thermal cycling conditions enabled all genotypes to be amplified with similar efficiency. The quantitative tests exhibited a linear range extending from 500 to 500,000 IU/ml and excellent reproducibility, with coefficients of variation ranging from 18 to 39%, within the linear range. These data indicate that the version 2. 0 AMPLICOR HCV tests will improve diagnosis of HCV infection and will yield more-accurate titers for prognosis and for monitoring therapeutic efficacy, particularly at low viral loads. Furthermore, it will be possible to compare the performance characteristics and viral load measurements of AMPLICOR tests to those of other tests that adopt the international unit as the standard of measurement.

[Implementation of a software for acquiring and analysing myoelectric potential signals in ergonomical research of space manual system]

Objective. A software used for acquiring and analyzing signals was developed for ergonomical research on Human Workload in space manual system. Method. As an important part of the whole experimental equipment and being developed in PC, the software is composed of acquisition and display program, analysis and processing program and data files. Result. The software is capable of making realtime acquisition and display of four channels of myoelectric potential signals and one channel of operation signal synchronously. The signals are then analyzed and processed off-line. Conclusion. During the development, its realtime feature was implemented by means of some technical methods, such as that different machine assigned to view-scenery display and signal acquisition, different frequency assigned to EMG signal and operation ones, and different cycle assigned to acquisition, display and storage. Above all, with friendly man-machine interface and high accuracy of data, the software was even reliable.

The role of cellular glutathione peroxidase redox regulation in the suppression of tumor cell growth by manganese superoxide dismutase

Manganese-containing superoxide dismutase (MnSOD) is an essential primary antioxidant enzyme that converts superoxide radical to hydrogen peroxide and molecular oxygen within the mitochondrial matrix. Cytosolic glutathione peroxidase (GPX) converts hydrogen peroxide into water. MnSOD is reduced in a variety of tumor types and has been proposed to be a new kind of tumor suppressor gene, but the mechanism(s) by which MnSOD suppresses malignancy is unclear. According to the enzymatic reactions catalyzed by MnSOD and cytosolic GPX, change in the cellular redox status, especially change attributable to accumulation of hydrogen peroxide or other hydroperoxides, is a possible reason to explain the suppression of tumor growth observed in MnSOD-overexpressing cells. To test this possible mechanism, we transfected human cytosolic GPX cDNA into human glioma cells overexpressing MnSOD. The results showed that GPX overexpression not only reversed the tumor cell growth inhibition caused by MnSOD overexpression but also altered the cellular contents of total glutathione, reduced glutathione, oxidized glutathione, and intracellular reactive oxygen species. Overexpression of GPX also inhibited degradation of the inhibitory subunit alpha of nuclear factor-KB. These results suggest that hydrogen peroxide or other hydroperoxides appear to be key reactants in the tumor suppression by MnSOD overexpression, and growth inhibition correlates with the intracellular redox status. This work suggests that manipulations that inhibit peroxide removal should enhance the tumor suppressive effect of MnSOD overexpression.

Protective effects of fructose-1,6-diphosphate against cerebral injury induced by subacute carbon monoxide intoxication in mice

AIM

To study the effects of fructose-1,6-diphosphate (FDP) on delayed cerebral injury in mice from subacute carbon monoxide (CO) exposure.

METHODS

Mice were exposed to CO (100 mL/kg i.p.) once a day, continouUsly for 7 d. After 7-d CO-exposure, mortality of mice, changes in learning ability and memory using passive avoidAnce test, the pathomorphologic observation of brain tissue slices, and changes in monoamine oxide (MAO)-B activities in cerebral tissue were studied. FDP was administrated 30 min before CO-exposure every time.

RESULTS

The preadministration of FDP markedly decreased the mortality of mice, almost reversed the impairment of learning and memory function, prevented the cells from delayed death in hippocampal neurons and blunted the rise in MAO-B activity after subacute CO poisoning of mice.

CONCLUSION

FDP pretreatment markedly prevented mice from delayed encephalopathy after CO poisoning.

Characterization of murine Th1 clones specific to egg antigen of Schistosoma japonicum and their interaction with cytokines

T cell clones (B1, B21, B7, A25) specific to the soluble egg antigen (SEA) of Schistosoma japonicum were established from C3H/He mice immunized with SEA. These clones belonged to CD3+, CD4+ and CD8-Th1 cells, showing TCR-gamma delta-, TCR-alpha beta+ and Vbeta10b+. The molecular weights of target antigens recognized by the clones ranged from 51 to 80 kDa. Interleukin-2 (IL-2) and IL-12 could vigorously increase the proliferation response of the T clones to SEA; while IL-10 and transforming growth factor-beta1 (TGF-beta1) strongly inhibited the response. IL-12 activity was detected in the culture supernatant of T clones stimulated with SEA in the presence of APC (antigen presenting cells). This stimulation also upregulated the expression of the IL-12 receptor on the T clones. IL-12 from APC served as a costimulatory factor for the SEA induced proliferation of the T clone cells. Clone B1 was able to induce granuloma formation both in vivo and in vitro. These data provide further insight into the complicated interaction among SEA, T cell and cytokine at a clonal level in S. japonicum infection.

Superoxide generation in v-Ha-ras-transduced human keratinocyte HaCaT cells

The oncogenic ras protein controls signal-transduction pathways that are critical for cell proliferation and tumorigenesis. Here, we demonstrate that v-Ha-ras-transduced human keratinocyte HaCaT cells produced significantly larger amounts of superoxide than did control cell lines. The superoxide generation was mediated by the transduced ras protein, because superoxide generation was modified by an inhibitor, lovastatin, that inhibits ras farnesylation during ras protein maturation. Superoxide generation was also inhibited by diphenylene iodonium, an inhibitor of flavoproteins, including NADPH oxidase, but not by rotenone, an inhibitor of the respiratory chain of the mitochondria. Those observations suggested that a phagocytic-like NADPH oxidase exists in keratinocytes that could be activated by the dominant activated v-Ha-ras and produce superoxide. Overexpression of manganese-containing superoxide dismutase and copper and zinc-containing superoxide dismutase cDNA via adenovirus infection also attenuated superoxide generation. Previous work has demonstrated that extracellular superoxide dismutase (SOD) can lower superoxide generation; this is the first report that intracellular SOD could also modify the amount of superoxide production from the cells. This report implies that superoxide radical may act as a second messenger molecule of oncogenic ras.

Dynamic analysis of T-lymphocyte function in relation to hepatopathologic changes and effect of interleukin-12 treatment in mice infected with Schistosoma japonicum

We analyzed the dynamics of splenic T-lymphocyte function in relation to hepatopathologic changes in C3H/Hc mice, experimentally infected with Schistosoma japonicum. Vigorous granuloma formation was observed at 7 wk postinfection. At 10 wk postinfection, granuloma formation entered into the down-modulation stage, as represented by the diminished granuloma size. The Th2 response was activated when eggs appeared in the liver, whereas Th1 responses were depressed and the proliferation of T lymphocytes was decreased. The level of IgG antibodies to the worm and egg antigens rose continually after infection. Interleukin-12 treatment of infected mice inhibited Th2 responses and T-cell proliferation, decreased granuloma formation and fibrosis, but had no effect on the fecundity of the worms. These data suggest that egg deposition is the major factor driving Th2 responses, depressing Th1 cytokine expression as well as T-cell proliferation in S. japonicum-infected mice.

Induction of vigorous cytotoxic T-lymphocyte responses by live attenuated simian immunodeficiency virus

Although live attenuated vaccine strains of simian immunodeficiency virus (SIV) have proven highly effective in protecting macaques against challenge with pathogenic SIV strains, little is known about the mechanisms of protective immunity induced by these vaccines. We examined cytotoxic T-lymphocyte (CTL) responses against SIV in animals infected with SIVmac239delta nef (deficient in nef) or SIVmac239delta 3 (deficient in nef, vpr, and upstream sequences in U3). To enhance detection of SIV-specific CTL activity, we stimulated peripheral blood mononuclear cells with autologous B-lymphoblastoid cell lines which had been infected with recombinant vaccinia viruses expressing SIV proteins and subsequently inactivated with psoralen and UV light. Animals chronically infected with SIV239delta nef or SIV239delta 3 mounted vigorous CTL responses against the SIV Gag and Env proteins. This CTL activity was major histocompatibility class restricted and mediated by CD8+ T lymphocytes. CTL responses persisted at relatively high levels for more than 6 years after infection. Limiting dilution precursor frequency assays demonstrated that the frequency of SIV-specific CTLs was as high as 234 CTL precursors per 100,000 cells. Animals acutely infected with SIV239delta nef developed CTL activity by day 14 after infection, coincident with decreases in viral load. Animals acutely infected with SIV239delta 3 developed CTL responses within 4 weeks of infection. Thus, vaccination of juvenile or adult animals with SIV239delta nef or SIV239delta 3 results in the induction of a vigorous CTL response which arises early in the course of infection and persists for years after a single inoculation of virus.

Effect of IL-12 on granuloma formation induced by injected Schistosoma japonicum eggs

The regulatory functions of IL-12 on granuloma formation by the eggs of S. japonicum in the lungs of BALB/c mice were studied. Mice were injected i.v. with the eggs to induce the pulmonary granuloma. On days 0, 1, 2, 3, 7, 8 after injection, mice were injected i.p. with murine rIL-12 at a dose of 1 microgram day-1 (Group I) or 3 micrograms day-1 (Group II) or with PBS as a control (Group III). On day 10, all mice were sacrificed. The areas of pulmonary granulomas in histological sections were quantitatively measured by image analyser and the levels of mRNA for IL-10, IFN-gamma, IL-12 and IL-5 were assayed by reverse transcriptase PCR (RT-PCR). The results showed that the mean area per granuloma was significantly decreased in Groups I and II as compared with Group III. As for cytokine induction, IL-10- and IFN-gamma-specific bands appeared in Groups I and II, but not in Group III. Bands for IL-5 appeared in all groups, while bands for IL-12 were not detected in any group. It is suggested that IL-12 could inhibit the Th2 dominant granuloma formation induced by the eggs of S. japonicum.

Isolation and characterization of a monoclonal antibody binding to the extracellular domain of the flk-2 tyrosine kinase receptor

The flk-2 tyrosine kinase receptor is expressed on hematopoietic stem cells and on acute leukemias (AML and ALL). We have isolated a rat monoclonal antibody (71E1) that binds to this receptor with a relative affinity of 5 nM. The antibody immunoprecipitates both murine and human forms of flk-2 and can block receptor activation by its cognate ligand. In addition, 71E1 inhibits the in vitro proliferation of the murine leukemic cell line, M1, that expresses high levels of flk-2. These results suggest that 71E1 may have utility as both a reagent for elucidating the biological role of flk-2 in hematopoiesis and as an immunotherapeutic in the treatment of acute leukemias.

[Relation between histo-compatibility antigen immunogenetics and pregnancy induced hypertension]

Fourty cases with pregnancy induced hypertension (PIH) and 100 normal pregnant women were selected for this study. The distribution of histo-compatibility antigen D region (HLA-DR) frequency, the frequency of homozygosity and the HLA-DR antigens sharing between partners were investigated. The results showed that the frequency of HLA-DR4 was significantly higher in PIH than that in normal pregnancy (P < 0.001). There was a very high DR antigen sharing between partners in PIH as compared to normal pregnancy (P < 0.01), specially obvious in the frequency of DR4 antigen sharing in PIH (P < 0.0001). There was, however, no significant difference in the frequency of homozygosity or heterozygosity between HLA-DR and DR4 locus. This study suggested that HLA-DR4 may be related to the genetic susceptibility of PIH. This correlation is presumably due to a linkage imbalance of susceptible gene of PIH and DR4, but whether DR4 acts directly as an immunodeficient gene remains to be determined.

[Breast-feeding in reducing regular insulin requirement in postpartum for insulin dependent diabetes mellitus and gestational diabetes mellitus]

From Jan. 1987-Jun. 1993, 37 cases of insulin dependent diabetes mellitus (IDDM) pregnant women and 10 gestational diabetes mellitus (GDM) mothers requiring regular insulin (RI) treatment during pregnancy were recruited. A comparative study of the daily RI requirement was carried out in women breast-feeding (BF) or not (non-BF) at different periods: before pregnancy, during gestation, postpartum and at present. Results showed no difference of RI requirement between BF and non-BF groups before pregnancy, during gestation and currently, but a significant decrease of RI requirement (P < 0.05) among BF mothers in postpartum period. Of the 10 GDM cases, 3 of them who did not breast feed their babies required further RI for 4-7 days in the postpartum period, whereas 7 BF mothers did not need any RI after delivery with blood glucose levels remaining within normal range. Based on the above analysis one may conclude that BF can reduce the RI requirement of IDDM and GDM mothers in the postpartum period. It is thought that more energy is needed in the process of producing milk, and serum glucose is the main substance for lactose synthesis, thus blood glucose level of BF mother is decreased, and so is the RI requirement. Therefore, mothers with diabetes mellitus are encouraged to breast feed their babies.

HLA-DR and -DQB1 genotyping in a Chinese population

Using molecular biological methods, 58 unrelated Chinese from Shanghai were typed for HLA-DR and DQ. The Shanghai population possesses the principal HLA-DR and DQ characteristics of the oriental populations but with an increase of the DRB1*12 allele. So HLA typing of populations appears to be important not only for anthropological studies but also for transplantations and HLA associations with diseases.

The application of AmpliProbe in diagnostics

AmpliProbe System is a rapid, enzyme-labeled, non-isotopic probe system that has high sensitivity and flexibility. AmpliProbe System consists of two major components: target-specific "primary" probes and target-independent, enzyme-labeled, signal-generating "secondary" probes. The visualization of the complemental hybridization between the target DNA or RNA and probes is accomplished by an enzymatic chemiluminescent reaction. The AmpliProbe System format allows hybridization and signal visualization to be completed within five to seven hours. In this paper we present several successful applications of AmpliProbe in the detection of infectious disease pathogens and the detection of gene amplification and transcription elevation in the evaluation of oncogenes in cancer research.

Endoscopic lithotripsy of gastric bezoars using a laser-ignited mini-explosive device

This paper reports the successful experiences of in vitro and in vivo studies on endoscopic fragmentation of gastric bezoars using a laser-ignited mini-explosive device. This new technique has been used clinically in 31 patients with gastric bezoars since January 1988. All patients were completely cured without any complication. The relationship between gastric bezoars and ulcers, and the technique of treatment were discussed.

A cis-acting element in the promoter region of the murine c-myc gene is necessary for transcriptional block

A block to elongation of transcription has been shown to occur within the first exon of the human and murine c-myc genes. The extent of this block was found to vary with the physiological state of cells, indicating that modulation of the transcriptional block can serve to control the expression of this gene. To determine which sequences are required in cis for the transcriptional block, we generated a series of constructs containing various portions of murine c-myc 5'-flanking and exon 1 sequences. We established populations of HeLa and CV-1 cells stably transfected with these constructs. The transcription start sites were determined by S1 nuclease mapping analysis, and the extent of transcriptional block was measured by nuclear run-on transcription assays. Our results demonstrate that at least two cis-acting elements are necessary for the transcriptional block. A 3' element was found to be located in the region where transcription stopped and showed features reminiscent of some termination sites found in procaryotes. A 5' element was positioned between the P1 and P2 (C. Asselin, A. Nepveu, and K. B. Marcu, Oncogene 4:549-558, 1989). Removal of the more 3' binding site abolished the transcriptional block.

Experimental and clinical investigation on oxiconazole

A new antimycotic imicazole drug, oxiconazole, used both in vitro and in vivo in the treatment of 212 cases of tinea corporis, tinea cruris and tinea pedis is reported. In vitro, it shows marked antimycotic effect against 24 strains of pathogenic fungi except those of Wangiella dermatitides and 3 strains of Aspergilli. The minimal inhibition concentration (MIC) to Epidermophyton floccosum and Candida guilliermondi are 1 microgram/ml and 0.5 microgram/ml. The cure rate of 2% cream of oxiconazole in 124 cases of tinea corporis and tinea cruris is 90.3%, and in 88 cases of tinea pedis, 89.78%.

Translocated c-myc genes produce chimeric transcripts containing antisense sequences of the immunoglobulin heavy chain locus in mouse plasmacytomas

Immunoglobulin heavy chain gene antisense transcripts contribute to the expression of translocated c-myc genes in several murine plasma cell tumors. These novel, chimeric transcripts comprise 5-50% of steady-state c-myc mRNA. Two transcripts isolated as cDNA clones use the normal splice donor and acceptor sites within the c-myc first intron. Another cDNA clone has the potential for encoding two types of c-myc proteins. The significance of immunoglobulin heavy chain gene antisense transcripts and transcriptional competence of the immunoglobulin heavy chain locus for c-myc expression is discussed.

Absence of somatic mutation in the variable region of MPC 11 variants expressing a different heavy chain isotype

Somatic mutation of immunoglobulin variable regions contributes to the diversity of the immune response. Some investigators have postulated that somatic mutation is coupled to isotype switching; others have presented evidence that the two processes are not linked. By using in vitro variants of the MPC 11 mouse myeloma cell line that produce heavy chains of different isotypes, we have examined several VH regions at the nucleotide level using a variety of different sequencing procedures. We have found no evidence of somatic mutation and conclude that the processes of somatic mutation and isotype switching may be independent.

Absence of somatic mutation in the variable region of MPC 11 variants expressing a different heavy chain isotype

Somatic mutation of immunoglobulin variable regions contributes to the diversity of the immune response. Some investigators have postulated that somatic mutation is coupled to isotype switching; others have presented evidence that the two processes are not linked. By using in vitro variants of the MPC 11 mouse myeloma cell line that produce heavy chains of different isotypes, we have examined several VH regions at the nucleotide level using a variety of different sequencing procedures. We have found no evidence of somatic mutation and conclude that the processes of somatic mutation and isotype switching may be independent.

The first exon of the c-myc proto-oncogene contains a novel positive control element

We have identified a positive modulator within the c-myc first exon downstream of the gene's transcription initiation sites, P1 and P2. We introduced myc-CAT (chloramphenicol acetyltransferase) hybrid genes into three cell lines (BJAB, COS and HeLa) and measured their expression by either CAT enzymatic activity, S1 nuclease protection or by a nuclear 'run-on' transcription assay. Removal of 46 bp from the 3' end of the first exon results in a decrease of myc-CAT expression and P2 activity. A 438-bp exon 1 segment, lacking the normal myc promoters, efficiently drives the expression of SV40 early promoters. We find that this first exon segment efficiently functions as a positive modulator only in its sense orientation, 3' of a nearby promoter. The positive effects of the myc first exon and the SV40 enhancer are complementary.

Deregulation of the c-myc oncogene in virus-induced thymic lymphomas of AKR/J mice

A high frequency (greater than or equal to 65%) of thymomas induced by mink cell focus-forming virus 69L1 in AKR/J mice contain proviral integrations which are clustered 0.7-kilobase upstream of the c-myc oncogene predominantly in the opposite transcriptional orientation. Blot hybridization experiments showed that on the average there was only a twofold elevation of steady-state c-myc RNA in the thymomas as compared with levels in normal AKR/J thymocytes. Such an increase would not appear to be sufficient as a mechanism of oncogene activation in this system. In contrast, S1 nuclease analysis of transcripts initiated from the two known c-myc promoters indicated a strong shift in promoter usage in virtually all thymomas tested. In normal thymus the ratio of transcripts initiated from the proximal promoter P1 to the distal promoter P2 was 0.2 to 0.3. In contrast, most of the thymomas tested (18 of 23) showed an average P1/P2 ratio of 1.2 regardless of whether or not proviral integrations could be detected within a 21-kilobase EcoRI fragment containing the three c-myc exons. We conclude that alterations in P1/P2 ratios are good indicators of c-myc deregulation in thymic lymphomas.

A negative transcriptional control element located upstream of the murine c-myc gene

We have investigated the nature of regulatory sequences within the vicinity of the murine c-myc locus by analyzing the expression of myc-chloramphenicol acetyl transferase (CAT) vectors transfected into a human lymphoblastoid cell line (BJAB) and a monkey fibroblast line (COS). CAT enzymatic assays and S1 nuclease protection experiments reveal that a negative element resides 428-1188 bp 5' of the first c-myc promoter, P1. This 760-bp segment of 5'-flanking c-myc DNA dramatically inhibits CAT gene expression in the pSV2CAT vector when placed in either orientation approximately 1.7 kb 3' (and approximately 3.2 kb 5' on the circular plasmid) from the SV40 promoter region. By employing this strategy, we were unable to identify an analogous DNA segment that is closer to or within the first c-myc exon. We propose that this 5' c-myc region be termed a 'dehancer' since this negative element has the opposite properties of a transcriptional enhancer.

Amplification and altered expression of the c-myc oncogene in A-MuLV-transformed fibroblasts

Chromosomal rearrangements involving the c-myc oncogene are a prevalent feature of plasmacytomas that arise after inoculating BALB/c mice with pristane and Abelson murine leukaemia virus (A-MuLV). With this observation in mind, we decided to determine if any genetic alterations of the c-myc locus could be observed in cells of a different type, when transformed in vitro by A-MuLV. Here we have analysed three independent A-MuLV-transformed NIH 3T3 lines (ANN-I, 54c12 and N25), and found that the c-myc locus is amplified 8-19-fold in each transformant. Quantitative S1 nuclease mapping performed on ANN-I and 54c12 RNAs demonstrated that: (1) c-myc messenger RNAs accumulated to double the levels found in NIH 3T3 cells; and (2) a shift in the use of the two normal c-myc transcription initiation sites (P1 and P2) occurred in favour of the 3' site, P2. Analysis of c-myc chromatin by DNase I treatment of 54c12 nuclei revealed that most, if not all, of the c-myc gene copies were transcriptionally competent. We present alternative ideas to explain why amplification of the c-myc gene occurs repeatedly in A-MuLV-transformed fibroblasts. Finally, we discuss our results in relation to the hypothesis linking the phenomenon of tumour progression with the amplification of oncogenes.

Posttranscriptional mechanisms are responsible for accumulation of truncated c-myc RNAs in murine plasma cell tumors

c-myc Messenger RNAs are known to be extremely unstable (t1/2 = 10 min) in normal and tumor cells, suggesting that degradation could play an important role in regulating their steady state level in the cytoplasm. We have investigated the stabilities of c-myc mRNAs in three murine plasmacytomas, where the c-myc gene either remains intact (ABPC20) or exists in a truncated form (MPC-11 and J558L) subsequent to 6;15 or 12;15 chromosome translocations respectively, and in an A-MuLV-induced pre-B lymphoma line (18-81.5) that lacks chromosome translocations and contains both c-myc genes in their normal context. The truncated myc genes in J558L and MPC-11 lack the promoters of the normal gene but are transcribed from cryptic promoters within the first c-myc intron. We found that posttranscriptional processes are largely responsible for the higher steady state accumulations of truncated c-myc transcripts, while broken and intact c-myc genes are transcribed at comparable rates.

Chromosome translocations clustered 5' of the murine c-myc gene qualitatively affect promoter usage: implications for the site of normal c-myc regulation

Five novel murine plasma cell (PC) tumors with chromosome translocations 350-500 bp 5' of the first c-myc exon are described. The t(12;15)s of TEPC 1194, ABPC 33 and TEPC 1165 position the intact c-myc locus 5' of the Cu, C gamma 2a and C alpha IgCH genes respectively. In ABPC 17, the IgH enhancer element and adjacent switch (Su) sequences were found 5' of the first c-myc exon while this enhancer is associated with the reciprocal products of the TEPC 1194, ABPC 33 and TEPC 1033 translocations. Quantitative S1 nuclease analyses demonstrate that the ratios of transcription from the two c-myc promoters (P1 and P2) are increased 4-to 7-fold in these five tumors. With the exception of TEPC 1165, (which contains a small deletion in exon 1), such increases in P1:P2 ratios appear to be manifested by a reduction in P2 usage in comparison to other tumors without such promoter shifts. A survey of 27 additional PC and non-PC B lymphoid tumors and cell lines revealed that myc promoter shifts of this magnitude are unique to PC tumors with 5'-proximal translocations. We propose that (i) these clustered breakpoints identify a normal c-myc regulatory element located at least 350 bp 5' of c-myc exon 1; (ii) the loss or disruption of this cis-acting upstream element and the linkage of c-myc to the IgCH locus would result in abnormal expression of this oncogene in these as well as most other PC tumors.