Neuroendocrine carcinoma of the sigmoid colon: report of a case

Neuroendocrine carcinoma of the colon is a rare entity; however, this type of tumor is known for its aggressive progression and poor prognosis. A case of a 56-year-old Japanese male is presented in this report. A huge, child's head-sized tumor was found to have grown extraluminally on the sigmoid colon with multiple liver metastases. The tumor measured 16.5 x 15 x 8.2 cm in size and weighed 1 300 g. The patient died of hepatic failure due to massive liver metastases 6 months after operation. The pathological findings including an electron microscopic analysis were correlated with those of neuroendocrine carcinoma. We reviewed the English literature, and analyzed 94 cases of neuroendocrine carcinoma which had been reported previously. The nomenclature and definition of this disease still remains somewhat unclear, and not a small population of this disease may thus have been misdiagnosed and treated as other less aggressive entities. The necessity to make an accurate differential diagnosis in such cases is thus emphasized.

Antiplatelet and antithrombotic activities of NQ301, 2-chloro-3-(4-acetophenyl)-amino-1,4-naphthoquinone

The antiplatelet and antithrombotic activities of a newly synthesized NQ301, 2-chloro-3-(4-acetophenyl)-amino-1,4-naphthoquinone, were investigated on human platelet aggregation in vitro and rats ex vivo, and murine pulmonary thrombosis in vivo. NQ301 potently inhibited ADP-, collagen-, epinephrine- and calcium ionophore A23187-induced human platelet aggregation in a concentration-dependent manner in vitro. NQ301 significantly inhibited platelet aggregation in orally administered rats ex vivo. NQ301 prevented death due to pulmonary thrombosis in mice dose-dependently in vivo. NQ301 also showed significant prolongation of tail bleeding time in conscious mice. However, NQ301 did not alter such coagulation parameters as activated partial thromboplastin time, prothrombin time, and thrombin time in human plasma. These results suggest that NQ301 may be a promising antithrombotic agent, and the antithrombotic activity of NQ301 may be due to antiplatelet aggregation activity but not to in vitro anticoagulation.

Evaluation of different methods for cleaning and preparing occlusal fissures

The effectiveness of different methods for cleaning and preparing occlusal fissures before placing sealants was evaluated. Extracted mandibular molars received such treatments as brushing, pumicing, bur preparing, and air abrasion before application of fissure sealants. FluroShield fissure sealant was then applied to the occlusal fissures. Specimens were subjected to thermo-cycling and then immersed in a 10% solution of methylene blue, and finally sectioned. The sections were examined and photographed in a stereomicroscope, and the dye penetration was recorded using a scoring system. The results indicated that only the control (brushing with a dry brush) and the pumicing groups demonstrated dye penetration to the base of the sealant. Teeth prepared with the #1/4 round bur and air abrasion demonstrated a better seal in evaluated fissures. For this study, those three groups (occlusal fissures prepared with the #1/4 round bur and two air abrasion methods), demonstrated significantly better sealing (P < 0.01) than the control group and the other groups tested.

Antithrombotic activities of green tea catechins and (-)-epigallocatechin gallate

The antithrombotic activities and mode of action of green tea catechins (GTC) and (-)-epigallocatechin gallate (EGCG), a major compound of GTC, were investigated. Effects of GTC and EGCG on the murine pulmonary thrombosis in vivo, human platelet aggregation in vitro, and ex vivo, and coagulation parameters were examined. GTC and EGCG prevented death caused by pulmonary thrombosis in mice in vivo in a dose-dependent manner. They significantly prolonged the mouse tail bleeding time of conscious mice. They inhibited adenosine diphosphate- and collagen-induced rat platelet aggregation ex vivo in a dose-dependent manner. GTC and EGCG inhibited ADP-, collagen-, epinephrine-, and calcium ionophore A23187-induced human platelet aggregation in vitro dose dependently. However, they did not change the coagulation parameters such as activated partial thromboplastin time, prothrombin time, and thrombin time using human citrated plasma. These results suggest that GTC and EGCG have the antithrombotic activities and the modes of antithrombotic action may be due to the antiplatelet activities, but not to anticoagulation activities.

Vascular endothelial growth factor expression in preoperative biopsy specimens correlates with disease recurrence in patients with early gastric carcinoma

BACKGROUND

Recently many studies have demonstrated that the degree of tumor angiogenesis is related to the aggressiveness of the tumor and clinical outcome. Vascular endothelial growth factor (VEGF) is a well characterized inducer of angiogenesis. In this study, the authors investigated the prognostic significance of VEGF expression in patients with early gastric carcinoma together with p53 gene abnormality and tumor cell proliferation.

METHODS

One hundred ninety-five endoscopically biopsied specimens obtained preoperatively from patients with early gastric carcinoma were studied immunohistochemically.

RESULTS

According to conventional clinicopathologic factors, submucosal invasion, lymph node metastases, and tumor size were associated significantly with the incidence of disease recurrence. According to conventional biologic factors, VEGF expression was observed more frequently in patients with disease recurrence compared with those without disease recurrence whereas neither p53 abnormality nor tumor cell proliferation were correlated with prognosis. Moreover, multivariate analysis indicated that VEGF expression (as well as submucosal invasion and lymph node metastases) is an independent predictor of disease recurrence.

CONCLUSIONS

The results of the current study show that VEGF expression may be a useful prognostic factor for patients with early gastric carcinoma.

Vascular endothelial growth factor expression in preoperative biopsy specimens correlates with disease recurrence in patients with early gastric carcinoma

BACKGROUND

Recently many studies have demonstrated that the degree of tumor angiogenesis is related to the aggressiveness of the tumor and clinical outcome. Vascular endothelial growth factor (VEGF) is a well characterized inducer of angiogenesis. In this study, the authors investigated the prognostic significance of VEGF expression in patients with early gastric carcinoma together with p53 gene abnormality and tumor cell proliferation.

METHODS

One hundred ninety-five endoscopically biopsied specimens obtained preoperatively from patients with early gastric carcinoma were studied immunohistochemically.

RESULTS

According to conventional clinicopathologic factors, submucosal invasion, lymph node metastases, and tumor size were associated significantly with the incidence of disease recurrence. According to conventional biologic factors, VEGF expression was observed more frequently in patients with disease recurrence compared with those without disease recurrence whereas neither p53 abnormality nor tumor cell proliferation were correlated with prognosis. Moreover, multivariate analysis indicated that VEGF expression (as well as submucosal invasion and lymph node metastases) is an independent predictor of disease recurrence.

CONCLUSIONS

The results of the current study show that VEGF expression may be a useful prognostic factor for patients with early gastric carcinoma.

Vascular endothelial growth factor expression in preoperative biopsy specimens correlates with disease recurrence in patients with early gastric carcinoma

BACKGROUND

Recently many studies have demonstrated that the degree of tumor angiogenesis is related to the aggressiveness of the tumor and clinical outcome. Vascular endothelial growth factor (VEGF) is a well characterized inducer of angiogenesis. In this study, the authors investigated the prognostic significance of VEGF expression in patients with early gastric carcinoma together with p53 gene abnormality and tumor cell proliferation.

METHODS

One hundred ninety-five endoscopically biopsied specimens obtained preoperatively from patients with early gastric carcinoma were studied immunohistochemically.

RESULTS

According to conventional clinicopathologic factors, submucosal invasion, lymph node metastases, and tumor size were associated significantly with the incidence of disease recurrence. According to conventional biologic factors, VEGF expression was observed more frequently in patients with disease recurrence compared with those without disease recurrence whereas neither p53 abnormality nor tumor cell proliferation were correlated with prognosis. Moreover, multivariate analysis indicated that VEGF expression (as well as submucosal invasion and lymph node metastases) is an independent predictor of disease recurrence.

CONCLUSIONS

The results of the current study show that VEGF expression may be a useful prognostic factor for patients with early gastric carcinoma.

The changes of ventilatory parameters in laparoscopic colecystectomy

We investigated the ventilatory changes in healthy patients without cardiopulmonary pathology during elective laparoscopic cholecystectomy in the head-up position. During surgery, intraabdominal pressure was maintained at 15 mmHg by a CO2 insufflator, and minute ventilation was controlled with a constant tidal volume and fixed respiratory rate. PETCO2 was monitored continuously and recorded every minute. Basic hemodynamic and ventilatory parameters were measured before anesthesia; after induction of anesthesia; at 5 min, 10 min and 30 min after peritoneal insufflation; and 5 min and 10 min after exsufflation. Arterial blood samples were obtained 3 times to calculate D(a-A)CO2, VD/VT, and Vco2. The latent period of PETCO2 change was 2.9 min, the ascending period was 12.6 min, and the descending period was 12.2 min. During the 71.5 min of pneumoperitoneum, V(I), VE, peak and plateau Paw increased, while Cdyn decreased significantly. Peritoneal insufflation or exsufflation also resulted in a significant change of D(a-A)CO2, D(a-A)O2, and Vco2. The anesthesiologist must be aware of both hemodynamic and ventilatory changes and must be ready to respond promptly and adequately.

Matrix metalloproteinase-1 expression is a prognostic factor for patients with advanced gastric cancer

Proteolytic activity of cancer cells is an important factor in metastasis. This study examined the relationship between MMP-1 expression of gastric cancer cells and peritoneal metastasis. MMP-1 expression was found in 76/103 (75.2%) cases examined and was significantly associated with both peritoneal metastasis and lymph node metastasis (p<0.05, respectively). The prognosis of patients with MMP-1 positive tumor was significantly worse than that of patients with MMP-1 negative tumor (p<0.05). These findings suggested that MMP-1 might be a prognostic factor in case of advanced gastric cancer and might be useful in determining whether or not adjuvant therapy was indicated for patients at high risk of peritoneal recurrence.

Degeneration and transdifferentiation of human lens epithelial cells in nuclear and anterior polar cataracts

PURPOSE

To study the possible mechanisms of cataractogenesis by evaluating the characteristics of cataractous lens epithelial cells (LECs) in different types of human cataract.

SETTING

Kangnam St. Mary's Hospital, The Catholic University of Korea, Seoul, Korea.

METHODS

Lens epithelial cells attached to the anterior capsules in eyes with nuclear or anterior subcapsular were analyzed for morphological characteristics by electron microscopy and for cellular characteristics by immunohistochemistry.

RESULTS

Human LECs beneath the anterior capsule were degenerated in nuclear cataracts and were transdifferentiated in anterior polar cataracts. In senile nuclear cataractous lenses, LECs beneath the anterior capsule showed degenerative changes in morphology. In nuclear cataracts, LECs were immunohistochemically positive for cytokeratin and vimentin, while those in anterior polar cataracts were positive for vimentin only. The LECs of anterior subcapsular cataracts were transdifferentiated into spindle-shaped fibroblast-like cells without cellular junctions and embedded within a fibrillar meshwork mass. The extracellular matrixes in the anterior capsule of anterior subcapsular cataracts were immunohistochemically positive for fibronectin, laminin, collagen type I, and collagen type IV.

CONCLUSIONS

Lens epithelial cells in different types of cataracts have distinct cellular characteristics and may possess a bipotential nature with the ability to transdifferentiate into mesenchymal cells. This may be an underlying mechanism for the development of cataract and capsule opacification.

Radiopacity of tantalum oxide nanoparticle filled resins

OBJECTIVES

Radiopacity of composite resins allows radiographic distinction of existing restorations and recurrent caries. Current composites must be supplemented with heavy metal-containing glasses or minerals to achieve a desired radiopacity. The purpose of this study was to evaluate the radiopacity of Tantalum oxide (Ta2O5) filled resins at varying percentage loadings.

METHODS

Methacrylate functionalized Ta2O5 nanoparticles (< 50 nm) in methanol-dissolved or powder forms were mixed into either glycerol dimethacrylate (GDMA) or a bisGMA, TEGDMA, bisEMA mixture (GTE). Specimens were made in a split brass mold (2 x 2 x 15 mm) and compared with an aluminum stepwedge (99.5% pure Al) and a dentin slice of the same thickness. Kodak Ultraspeed periapical X-ray film on a lead plate at a target distance of 45 cm was exposed at 70 kVp and 10 mA, for 0.5 s and processed automatically. Optical density was measured (n = 3) with an RMI Processor Control Densitometer. Radiopacity was calculated as percent relative linear attenuation coefficient (Alpha). ANOVA and Student-Newman-Keuls comparisons were used to determine significance at the 95% confidence level.

RESULTS

Radiopacity increased significantly with Ta2O5 loading (p = 0.001). Ta2O5 nanoparticle filled resins enter the optimal range of diagnostic detectability (alpha = 150-250) at 50 wt.% and approach equivalence with enamel at approximately 70 wt.%.

SIGNIFICANCE

The introduction of tantalum oxide nanoparticle filler has potential as a miscible component of a resin composite to provide radiopacity for microfiller-type restorative materials and to circumvent the need for hydrolysis-prone glass reinforcing fillers.

Radioimmunotherapy of orthotopically transplanted pancreatic cancer with 131I-labeled chimeric monoclonal antibody Nd2

Recombinant mouse/human chimeric antibody Nd2 was previously reported to have the same specificity and reactivity against pancreatic cancer as murine Nd2 without HAMA production which induced serious problems in clinical application. We established orthotopic SW1990 transplanted mice to represent the progression of pancreatic cancer. We examined anti-tumor effect of 131I-labeled chimeric Nd2 in an orthotopic transplant model. 131I-labeled chimeric Nd2 inhibited the growth of orthotopically transplanted tumors and extended the survival time of the mice. These results suggest that 131I-labeled chimeric Nd2 has high clinical applicability in the therapy of pancreatic cancer.

Expression of the mismatch repair gene hMSH2 in sporadic colorectal cancer

At least four genes involved in DNA mismatch repair (MMR), hMSH2, hMLH1, hPMS1 and hPMS2, have been cloned and characterized. These genes have been demonstrated to be altered in the germline of patients with hereditary non-polyposis colorectal cancer (HNPCC). HNPCC is an autosomal dominant disease characterized by a preponderance of proximal colon, young age of onset, increased multiplicity, and improved stage-specific survival. In this study, we examined the expression of hMSH2 protein in sporadic colorectal cancer (CRC). As a result, the frequency of right-sided CRC and multiple CRCs were significantly higher in the patients with hMSH2-negative CRC than in those with hMSH2-positive CRC. The rate of p53 positivity was significantly lower in the hMSH2-negative tumours than that in the hMSH2-positive tumours. The disease-free survival rate tended to be higher in the patients with hMSH2-negative CRC than in the patients with hMSH2-positive CRC. Our findings suggest that both the clinicopathological and biological features of hMSH2-negative sporadic CRC seemed to be similar to those of HNPCC. To clarify the mechanism of carcinogenesis in HNPCC and sporadic CRC, further investigations of genetic alterations caused by MMR genes will be needed.

Thymidine phosphorylase activity in tumor correlates with venous invasion

Thymidine phosphorylase (dThdPase) is identical to platelet-derived endothelial cell growth factor (PD-ECGF), an angiogenesis factor. We investigated the correlation between dThdPase activity in gastric cancer tissue and clinicopathological factors. Thirty-three cancer tissue specimens and 23 adjacent normal gastric mucosal specimens were obtained from surgery. Measurement of dThdPase activity was based on the amount of 5-fluorouracil formed from 5'-deoxy-5-fluorouridine by dThdPase. Mean dThdPase activity in cancer tissue was approximately 3.2 times higher than that in normal tissue. Cancerous tissues with venous invasion had about twice the dThdPase activity as cancerous tissues without venous invasion. Other clinicopathological features were not related to dThdPase activity. A correlation between dThdPase activity and immunosuppressive acidic protein level was observed (r = 0.532, P = 0.005). dThdPase activity in gastric cancer cells was found to be correlated with venous invasion, supporting previous findings that it plays a role in tumor angiogenesis.

Granular cell tumor of the duodenum: a case report

Granular cell tumor (GCT) in the duodenum is an extremely rare disease: only one case has been listed in a review, to date. We reported a 47-yr-old Japanese male case with GCT of the duodenum. Clinically, melena caused by bleeding from the tumor was the only symptom. The tumor cells showed abundant, granular eosinophilic cytoplasm. Although this tumor was clinically and histologically benign, highly developed tumor microvessels were demonstrated both angiographically and histologically, suggesting malignant potential of the tumor.

p53 protein overexpression as a predictor of the response to chemotherapy in gastric cancer

This study was performed to evaluate p53 overexpression as a predictor of the response to chemotherapy of patients with gastric cancer. The subjects comprised 20 patients with Stage IV gastric cancer and three with locally recurrent lesions, all of whom were treated with 5-fluorouracil (5-FU) plus cisplatin (CDDP) for 4 weeks. Of the total 23 patients there were 10 responders; 2 showing complete response (CR) and 8, partial response (PR). Specimens obtained by endoscopic biopsy were immunohistochemically stained using anti-p53 protein and bcl-2 protein antibody. Of the 10 responders, 7 demonstrated negative p53 staining, and of the 13 nonresponders, 11 demonstrated positive p53 staining (P = 0.013). Tissue from 3 of the responders and 7 of the nonresponders that stained for bcl-2 were positive prior to chemotherapy; however, there was no association between bcl-2 staining and chemotherapeutic effect. In conclusion, immunohistochemical identification of p53 in pretreatment tissue may represent a useful predictor for chemotherapeutic outcome in patients with gastric cancer.

Purification and molecular cloning of a platelet aggregation inhibitor from the snake (Agkistrodon halys brevicaudus) venom

A platelet glycoprotein IIb-IIIa (GP IIb-IIIa) antagonist, salmosin, was purified to homogeneity from Korean snake (Agkistrodon halys brevicaudus) venom by means of chromatographic fractionations. We have isolated the cDNA encoding salmosin by using the cDNA library of the snake venom gland and analyzed its complete nucleotide sequence. The molecular identity was confirmed by comparison of the deduced amino acid sequence with the directly determined primary structure of salmosin. This protein is a single-chain polypeptide composed of 73 amino acids including 12 cysteines as well as the sequence Arg-Gly-Asp, a proposed recognition site of adhesive proteins. The primary sequence of salmosin shows considerable homology to previously described proteins of snake venom GP IIb-IIIa antagonist family. A molecular mass of 7474 for the protein was determined by matrix-assisted laser desorption ionization mass spectrometry. Salmosin inhibits GP IIb-IIIa binding to immobilized fibrinogen with an IC50 of 2.2 nM and ADP-induced platelet aggregation with an IC50 of 131 nM, respectively. This work demonstrates the purification, characterization, and cDNA cloning of salmosin, a platelet aggregation inhibitor that may have therapeutic potential as an antithrombotic agent.

Changes in tumor marker levels as a predictor of chemotherapeutic effect in patients with gastric carcinoma

BACKGROUND

Evaluating chemotherapeutic effect in patients with gastric carcinoma sometimes is difficult. The authors investigated whether changes in the serum levels of three tumor markers can be used to predict the clinical outcome after chemotherapy.

METHODS

Thirty patients with advanced and recurrent gastric carcinoma were treated with continuous 5-fluorouracil and low dose cisplatin for 4 weeks. Thirteen patients were treated neoadjuvantly prior to gastrectomy. The serum levels of carcinoembryonic antigen, carbohydrate antigen 19-9, and sialyl-Tn antigen were measured prior to and after chemotherapy. Responders were defined as those in whom abnormal serum levels of all three markers decreased to at least 50% of the pretreatment values and remained stable for at least 1 month.

RESULTS

The tumor markers could be evaluated in 27 of 30 patients (90%). The median duration of survival for the 15 responders and 12 nonresponders was 17 months and 6 months, respectively. There was a significant difference in the median duration of survival between the responders and nonresponders using the log rank test (P=0.0005). In the patients who received neoadjuvant therapy, the eight responders had a significantly longer survival period than did the three nonresponders (P=0.018). Seven of the eight responders showed evidence of tumor destruction histologically whereas none of the three nonresponders did.

CONCLUSIONS

Changes in the serum levels of these tumor markers after chemotherapy may be an excellent prognostic indicator for patients with gastric carcinoma.

Serum soluble interleukin-2 receptor level as a prognostic indicator in gastric cancer

T lymphocytes, activated by interleukin 2 during an anti-tumour response, release soluble interleukin 2 receptors (sIL-2R) into the bloodstream. We analysed the prognostic value of the serum sIL-2R level in gastric cancer. Serum concentration of sIL-2R in 96 gastric cancer patients and 100 healthy control subjects' was measured by enzyme-linked immunosorbent assay. All survivors were followed for more than 50 months. Serum sIL-2R level was considered with respect to prognosis, clinicopathological factors, other tumour markers and peripheral blood cell count. Stage III and IV patients had significantly higher sIL-2R levels than lower stage patients and control subjects. Stage III and IV gastric cancer patients were divided into 'high' and 'low' slL-2R groups based upon the control subjects' serum sIL-2R mean value plus one standard deviation. The high group had a significantly worse prognosis than the low group, although clinicopathological features and treatments were similar. Multivariate analysis demonstrated that the serum sIL-2R level is an independent indicator. The sIL-2R level did not correlate with carbohydrate antigen 19-9, however it did correlate with carcinoembryonic antigen (r = 0.22) and with numbers of peripheral blood monocytes (r = 0.54). In conclusion, serum sIL-2R may predict the outcome of gastric cancer patients with stage III or IV disease.

Demographic characteristics of zipeprol-associated deaths in Korea

The abuse of zipeprol, an antitussive agent, was found to be most prevalent among young people in Korea. Because abusers take large doses of this drug for its hallucinogenic effects, fatalities from zipeprol overdose abuse have been on the rise since 1991. Since 1991, a total of 69 zipeprol-related deaths have occurred throughout the nation. A demographic study shows that in ninety six percent of cases involving ziperol alone, the victims were in their teens and twenties. The male/female ratio in zipeprol related death was 3.5:1. Most of these zipeprol-associated deaths occurred in the larger cities of Seoul and Inchon. The blood concentration of zipeprol ranged from 0.8 to 38.3 micrograms/mL in single drug involved deaths, while zipeprol varied from 0.1 to 35.3 micrograms/mL in zipeprol and dextromethorphan victims.

Stimulatory effects of high-fat diets on colon cell proliferation depend on the type of dietary fat and site of the colon

To compare the effects of various types of dietary fat on colon cell proliferation used as an intermediate biomarker for colon carcinogenesis, groups of 10 male Sprague-Dawley rats were fed one of four high-fat diets (45% of total calories from corn oil, butter, beef tallow, and fish oil) for three weeks. As a control, a low-fat diet (15% of total calories from corn oil) was fed to a separate group. Cell proliferation was measured by in vivo incorporation of bromodeoxyuridine into DNA in the proximal and distal colon. Total lipids in feces were measured by a gravimetric method. There were significant differences in colon cell proliferation among the diet groups, where the high corn oil diet stimulated cell proliferation in proximal and distal colon compared with the high fish oil diet (p < 0.05). The protective effect of the high fish oil diet on cell proliferation was similar to that of the low corn oil diet. The effects of high beef tallow and butter diets on colon cell proliferation were highly dependent on sites of the colon, because the hyperproliferative effects by these diets were found only in the distal colon (p < 0.05). Fecal total lipids and fecal lipid concentrations were significantly affected by the dietary fat sources, in that the groups fed the saturated fats, such as butter and beef tallow, excreted more lipids into feces than did the groups fed the unsaturated fats, such as corn oil and fish oil. Fecal lipids were significantly correlated to colon cell proliferation in the way that distal colon cell proliferation increases as fecal lipids increase. Therefore, these data suggest that high levels of dietary fats may not always promote colon carcinogenesis, and the effects may be dependent on the types of dietary fat and sites of the colon.

Hepatitis C virus E2 protein purified from mammalian cells is frequently recognized by E2-specific antibodies in patient sera

The envelope protein of hepatitis C virus (HCV) is composed of two membrane-associated glycoproteins, E1 and E2. To obtain HCV E2 protein as a secretory form at a high level, we constructed a recombinant chinese hamster ovary (CHO) cell line expressing a C-terminal truncated E2 (E2t) fused to human growth hormone (hGH), CHO/hGHE2t. The hGHE2t fusion protein was purified from the culture supernatant using anti-hGH mAb affinity chromatography at approximately 80% purity. The purified hGHE2t protein appeared to be assembled into oligomers linked by intermolecular disulfide bond(s) when density gradient centrifugation and SDS-polyacrylamide gel electrophoresis were employed. When the purified fusion protein was used for testing its ability to bind to antibodies specific for HCV by enzyme-linked immunosorbent assay, the protein was recognized by antibodies in sera from 90% of HCV-positive patients. Treatment of hGHE2t protein by beta-mercaptoethanol, but not by heat and SDS, significantly reduced its reactivity to the antibodies of patient sera, suggesting that intermolecular and/or intramolecular disulfide bonds are important for its ability to recognize its specific antibody and that the E2 protein contains discontinuous antigenic epitope(s).

The effects of sprue design on the roughness and porosity of titanium castings

PURPOSE

This study measured the effects of the sprue number and position on the roughness and porosity of cast titanium crowns.

MATERIAL AND METHODS

Twenty-four complete veneer crown wax patterns were fabricated on a stainless steel die with a 30-degree bevel finish line. Twelve wax patterns were sprued with one 8-gauge wax sprue and the remaining 12 were double sprued. All patterns were invested with a phosphate bonded investment. Castings were made with a titanium casting, according to the manufacturer's instructions, with commercially pure titanium (> 99.5%) ingots. The castings were carefully cleaned and the surface roughness was measured with a profilometer. The specimens were then embedded and sectioned. Internal porosities were quantified with photographs by computerized image analysis. Data were analyzed with an ANOVA and the Student's t test with a confidence level of 95%.

RESULTS

The roughness value of the occlusal third of the crowns for the single sprue group (Ra = 3.0 +/- 0.9 microns) was significantly higher than other measurements (p < 0.05). There were statistically significant differences in values of porosity areas between the single sprue group (1.5 +/- 0.7 mm2) and the double sprue group (0.2 +/- 0.2 mm2) (p < 0.01). The double sprue design resulted in a relatively smoother casting surface and less internal porosity than the single sprue design.

CONCLUSIONS

Improvements in the degree of roughness and porosity of titanium crown castings were the result of the double sprue design.

Bonding strengths of porcelain repair systems with various surface treatments

STATEMENT OF PROBLEM

Metal porcelain combined surfaces are often involved in the repairing of fractured porcelain fused to metal restoration.

PURPOSE

This study investigated the effect of surface treatments on the bonding strength of porcelain fused to metal prosthesis repair.

MATERIAL AND METHODS

Specimens (8 x 4 mm) were fabricated with Biobond II casting alloy and randomly divided into three surface groups: metal, porcelain, and metal-porcelain combined surface. Biobond porcelain system and commercially available porcelain repair systems were tested. The metal surface group was further divided into two subgroups: control and sandblasting treatment (Al2O3, 50 microns, 20 seconds). In the porcelain surface group, there were three subgroups: (1) control, (2) sandblasting, and (3) 9.5% hydrofluoric acid etching for 4 minutes. The metal-porcelain surface combined group was divided into three subgroups: (1) control, (2) sandblasting, and (3) sandblasting and etching. The manufacturer's instructions for repair systems were followed for specimen preparation. Shear bond strengths of 10 specimens for each subgroup were determined with a universal testing machine after storing in distilled water at 37 degrees C for 7 days. The data were analyzed with analysis of variance and Scheffé F-test at the 95% significance level.

RESULTS

The Liner-M repair system showed significantly greater strength than the other tested systems on the metal surface with or without sandblasting treatment (p < 0.05). On the porcelain surface, the strengths of sandblasting and etching subgroups ranged from 7.2 to 16.8 MPa, and 6.8 to 16.8 MPa, respectively. There were no significant differences in bond strengths between sandblasting and combined treatment of the metal-porcelain combined surface group (p > 0.05).

CONCLUSION

The results of this study suggest that metal substrates treated with sandblasting and porcelain treated with either hydrofluoric acid or sandblasting can increase repair strength.

On the Complexation of Cd(II) Ions with Polyacrylic Acid

Complexation of Cd(II) ions with polyacrylic acid has been studied potentiometrically and by 113Cd NMR spectroscopy. A Donnan model proposed by Marinsky (Marinsky, J. A., in "Ion Exchange and Solvent Extraction" (J. A. Marinsky and Y. Marcus, Eds.), Vol. 11, p. 237. Dekker, New York, 1993; Miyajima, T., in "Ion Exchange and Solvent Extraction" (J. A. Marinsky and Y. Marcus, Eds.), Vol. 12, p. 275. Dekker, New York, 1995) has been applied in order to correct for the electrostatic effect on the equilibria inherent in the polyelectrolyte nature of the polyions. The potentiometric studies showed that the bidentate ligand complex, (CdA2)0, is the dominant species, but the formation of monodentate ligand complex, (CdA)+, cannot be neglected at low degree of dissociation of the polyacid. The stability constants of the (CdA)+ and (CdA2)0 complexes have been determined to be approximately 3.2 x 10 and 1.6 x 10(2), respectively. These values are in good agreement with the stability constants of 4.1 x 10 and 1.0 x 10(2) for Cd(acetate) and Cd(glutarate) complexes, where acetate and glutarate ions are the monomer analog ligands of polyacrylic acid. The 113Cd NMR chemical shift change upon dissociation of the polyacid also indicates that the dominant complex is (CdA2)0, but (CdA)+ becomes more appreciable with the decreasing degree of dissociation of the polyacid.

Studies on the synthesis and structure-activity relationships of 2-(2-functionalized pyrrolidin-4-ylthio)-1 beta-methylcarbapenems

A series of new carbapenem derivatives, which have a pyrrolidin-4-ylthio group substituted with a hydroxyalkyl or carbamoyl group at the 2' position as the C-2 side chain, have been prepared. The antibacterial activity and the stability to renal dehydropeptidase-I of these compounds were investigated, and the structure-activity relationships were studied. Among these new carbapenems, (1R,5S,6S)-2-[(2S,4S)-2-¿(2-hydroxy)ethylmercaptomethyl¿pyrroli din-4 -ylthio]-6-[(1R)-I-hydroxyethyl]-1-methyl-1-carbapen-2-em-3- carboxylic acid (1a) showed the most potent and well balanced activity and was selected as a candidate for further evaluation.

Renal apoptosis and clusterin following ureteral obstruction: the role of maturation

PURPOSE

Unilateral ureteral obstruction (UUO) increases renal apoptosis as well as clusterin, which in turn is modulated by angiotensin II. The present study was designed to investigate the role of maturation in these responses.

MATERIALS AND METHODS

Neonatal and adult Sprague-Dawley rats underwent UUO or sham operation. Fourteen days later, renal apoptosis was quantitated by flow cytometry, and renal messenger RNA (mRNA) was quantitated for renin and clusterin. Apoptotic cells, macrophages, clusterin and Dolichos biflorus agglutinin were localized by immunohistochemistry.

RESULTS

Following ipsilateral UUO, renal DNA content increased in the adult but decreased in the neonate. Renal macrophage infiltration induced by UUO was 2-fold greater in adults than in neonates, while distal tubular apoptosis was 2-fold greater in neonatal than in adult kidneys. Unilateral ureteral obstruction markedly increased renal renin mRNA expression in the neonate, but not in the adult, while clusterin expression was greater in adults than in neonates. Clusterin was localized to some, but not all, distal tubules containing apoptotic cells.

CONCLUSIONS

We conclude that, compared with the adult, UUO in the neonate induces greater apoptosis, which in turn contributes to reduced renal DNA. This may be modulated by relative suppression of clusterin in the obstructed neonatal kidney due to greater activation of the renin-angiotensin system.

Efficacy of ciprofloxacin and dexamethasone in experimental pseudomonas endophthalmitis

To determine injection time and effective dose of ciprofloxacin in endophthalmitis and to evaluate the effectiveness of dexamethasone. In rabbits, Pseudomonas aeruginosa (2 x 10(4) CFU/0.1 ml) was inoculated intravitreally. At 6, 12, 18, 24 hours postinoculation, single intravitreal doses of ciprofloxacin (300 micrograms/0.15 ml or 100 micrograms/0.05 ml) alone or with dexamethasone (400 micrograms) were given. Electrophysiological and histologic measures were utilized to rate drug effectiveness. 300 micrograms ciprofloxacin was effective in killing P. aeruginosa at 6 and 12 hours postinoculation, but one hundred ug ciprofloxacin was not effective. 300 ug ciprofloxacin had no significant effect in killing P. aeruginosa at 18 hrs and 24 hrs postinoculation. Eyes treated with dexamethasone (400 micrograms) and ciprofloxacin (300 micrograms) at 6 hours postinoculation did not differ from eyes treated with ciprofloxacin alone. Cultures from eyes treated with dexamethasone and ciprofloxacin at 12 hours postinoculation were positive. Cultures from eyes treated with ciprofloxacin alone were negative. The failure of treatment at 18 hrs and 24 hrs postinoculation may be due to either an increased rate of clearance of drugs from the eyes or a reduced bactericidal effect of ciprofloxacin which could be altered by acidic pH, degree of hypoxia or bacterial counts. Dexamethasone had no beneficial effect in the treatment of P. aeruginosa endophthalmitis in the early phase.

Linear alkylbenzenesulfonates (LAS) of an urban stream in Korea

Profiles of alkyl homologues and isomers of LAS were monitored for an urban stream polluted with municipal wastewaters in Korea. Alkylchains of the stream LAS were shorter than commercial standards and higher I/E ratios were associated with lower LAS concentrations. These suggested a partial biodegradation of LAS in the stream. Higher LAS concentrations were observed in the upper stream. LAS levels were at their lowest during summer probably due to high precipitation and faster biodegradation rates. LAS contributed to about 29% of MBAS and could be used to roughly estimate BOD concentration of the stream.

Fetal sex as a risk factor for fetal distress leading to abdominal delivery

A retrospective analysis of perinatal information of 7,924 confinements in the calendar year of 1994 was performed to determine whether fetal sex was a significant risk factor for fetal distress in labour leading to abdominal delivery. The sex of the fetus (male) was a significant, independent, risk factor for Caesarean section (odds ratio = 1.26, 95% CI = 1.05 to 1.50). This increase was wholly attributable to the increased risk of having fetal distress in labour (odds ratio = 1.76, 95% CI = 1.32 to 2.34). Male fetuses are at higher risk of developing fetal distress during labour.

Arrested development of the neonatal kidney following chronic ureteral obstruction

PURPOSE

The purpose of this study was to investigate the role of growth-related peptides in the impairment of renal growth and development resulting from unilateral ureteral obstruction (UUO) in the neonatal rats.

MATERIALS AND METHODS

Sprague-Dawley rats underwent UUO or sham-operation in the first 48-hours of life, and kidneys were harvested 1 to 28 days later. Renal messenger RNA (mRNA) was quantitated for renin, transforming growth factor-beta 1 (TGF-beta 1) and epidermal growth factor (EGF). Renal interstitial volume was measured in Masson-trichrome-stained sections, and renin and alpha-smooth muscle actin (alpha-SM actin) distribution were determined by immunocytochemistry.

RESULTS

The normal developmental increase in renal mass and DNA content were suppressed in ipsilateral UUO and increased in the intact opposite kidney. Renal interstitial volume was increased more than 10-fold by ipsilateral UUO. Unilateral ureteral obstruction resulted in a sustained increased in ipsilateral renal renin mRNA and persistence of fetal renin distribution. Renin in the contralateral kidney was suppressed. Transforming growth factor-beta 1 expression increased progressively in the obstructed kidney, but decreased after 7 days in sham-operated kidneys. While renal EGF expression was undetectable in the normal sham kidney during the first 3 days of life, it increased steadily with maturation. However, EGF expression remained suppressed in the obstructed kidney. Whereas alpha-SM actin disappeared from the interstitium of normal rat kidneys by 15 days of age, it persisted in the obstructed neonatal kidney.

CONCLUSIONS

As revealed by changes in expression of growth-related peptides, neonatal UUO delays ipsilateral renal development, which may contribute to impaired renal growth.

Regulation of renal growth factors and clusterin by AT1 receptors during neonatal ureteral obstruction

Unilateral ureteral obstruction (UUO) in the neonate impairs growth of the ipsilateral kidney. Since renal renin expression is increased by UUO, we hypothesized that, by activation of AT1 receptors, angiotensin II (ANG II) regulates expression of transforming growth factor-beta 1 (TGF-beta 1) and epidermal growth factor (EGF) in the obstructed kidney. Sprague-Dawley rats underwent left UUO or sham operation within the first 48 h of life and received losartan, 40 mg.kg-1.day-1, or saline. After 14 days, steady-state renal mRNA was determined for renin, TGF-beta 1, EGF, and clusterin. Losartan reduced the DNA content of the intact kidneys but did not further decrease that of the obstructed kidney. Losartan increased renal renin expression and decreased EGF expression by 80%, regardless of UUO. In contrast, losartan reduced TGF-beta 1 expression by 34% in obstructed kidneys but did not affect TGF-beta 1 in intact kidneys. Losartan increased clusterin expression by 60% in obstructed kidneys and seven-fold in intact kidneys. We conclude that activation of the ANG II AT1 receptor is necessary for normal renal growth and that TGF-beta 1 is regulated by AT1 receptors in the obstructed, but not intact, kidneys. Through AT1 receptors, endogenous ANG II stimulates EGF and inhibits clusterin expression.

A study of bond strength of dentin bonding agents to human dentin

BACKGROUND

Marginal leakage of restoration induced by polymerization shrinkage of composite resin can be prevented if the dentin bonding agent is strong enough to counteract the force of polymerization shrinkage.

METHODS

Fifty molar teeth obtained due to periodontal problem were used in this investigation. Crown portion of the teeth was grounded perpendicular to the long axis of the teeth until a complete layer of dentin surrounded by enamel was created. The teeth were then mounted with dental stone, and divided into five groups randomly. Dentin bonding agent was applied to the dentinal surface and a gelatin capsule mold was used to apply composite resin material. After incubation, the bonded composite specimens were tested with Instron universal testing machine in order to determine the shear strength of the composite bonding result. The fracture patterns were examined with scanning electron microscope.

RESULTS

The Universal bond 3 combined with the AP.H composite exhibited the highest shear bond strength (10.76 MPa). The fracture pattern of the Universal Bond 3 combined with AP.H was mainly that of cohesive failure in the composite resin part instead of adhesive failure in the other groups tested.

CONCLUSIONS

The shear bond strength of these five dentin bonding agents ranged from 2.89MPa to 10.76MPa. The fracture pattern of the tested groups was mainly that of adhesive failure at the interface between dentin bonding agent and its corresponding composite resin instead of cohesive failure disclosed in the composite resin part of Universal Bond 3 combined with AP.H group.

Effects of finishing and polishing procedures on the surface texture of resin composites

OBJECTIVES

This study was designed to investigate the effects of finishing and polishing procedures on the roughness and color of resin composite surfaces.

METHODS

Four composites and three different polishing systems were evaluated. Forty disc (10 mm x 2 mm) specimens of each composite were prepared. Thirty of them were ground wet through 320-grit paper, and the ground surfaces were used as the base line for the finishing procedure. Ten Mylar-covered specimens were used as controls. A color meter was applied to determine the color differences and a roughness meter was used to measure the surface roughness (Ra).

RESULTS

Microfilled composite demonstrated significantly less roughness (p < or = 0.01) than hybrid composite systems as tested by ANOVA and Scheffé's tests. Polishing procedures produced a decrease in the roughness, ranging from 26 to 74%. Relative to the shade guide, the mean color difference values for all the composites after polishing were significantly greater than for the controls (p < or = 0.01) and ranged from 1.08 to 8.15 units. A positive relationship between mean color differences and Ra values was determined by regression analysis (r = 0.55).

SIGNIFICANCE

A Mylar strip can create a smoother surface than the other types of tested polishing procedures. Because of the greater values in color differences and surface roughness, the shades of tested resin composites were lighter after the polishing procedures. A custom-made shade guide is suggested based on the results of this study.

The luminance-response function of the dark-adapted rabbit electroretinogram

The Naka-Rushton equation of the form, R = Rmax I(n)/(I(n)+Kn), has been used to describe the b-wave luminance-response function of the scotopic electroretinogram. Rmax is the asymptotic value of the b-wave amplitude as a function of stimulus luminance I, K is the luminance that produces a b-wave amplitude that is one-half Rmax, and n is a dimensionless constant that controls the slope of the function. These three parameters are often used in research laboratories, since it can show selective changes in each parameter. The present study describes these parameters (Rmax = 354 +/- 28 uV, n = 0.80 +/- 0.06, log K = -2.26 +/- 0.15 log cd. sec/m2) and the values obtained from the derivative analysis of Naka-Rushton equation (Anastasi et al) in 20 normal pigmented rabbit eyes. However, Naka-Rushton equation accurately describes the function only at low to moderate flash luminances. At high flash luminances, a second amplitude increase appears in the function.

Hepatocellular carcinoma metastasizing to the brain and orbit: report of three cases

Hepatocellular carcinoma rarely metastasizes to the brain or orbit. We report 3 clinically manifest examples, one of which occurred in a 13-yr-old boy. In 2 cases the intracranial metastasis was the initial presenting lesion. The 2 cases of brain metastasis both presented with intracerebral hemorrhage. Light microscopic examination of these tumors revealed a trabecular hepatocellular carcinoma of Edmondson grade II with focal hemorrhage and necrosis. Their immunohistochemical profile was identical to that described for primary hepatocellular carcinoma. The differential diagnosis from other intracranial metastatic tumors is discussed.

Metal release from high-copper amalgams containing palladium

BACKGROUND

High-copper amalgam containing palladium has been successfully developed. However, the effect of palladium on the release of corrosion products remains unknown. We studied the effect of palladium addition on the electrochemical properties of amalgams by measuring the amount of the elements released from the experimental Pd-containing amalgams into Ringer's solution.

METHODS

A series of specimens of high-copper amalgams containing different concentrations of palladium, from 0.42 w% to 3.33 w% in the final amalgam, fabricated from a blend of traditional amalgam alloy and copper-silver-palladium ternary alloy, were subjected to free corrosion in Ringer's solution at 37 degrees C for 3 months. Aliquots of 10 microL of electrolyte were removed serially with time, and the concentrations of Ag, Sn, Cu, Pd and Zn were evaluated by graphite furnace atomic absorption technique. In addition, dissolved Hg was evaluated by cold vapor atomic absorption technique in the same aliquotes. Various kinds of commercial amalgam including traditional (Spheraloy), high-copper blends (Dispersalloy and Valiant-Ph.D.) and high-copper spherical (Valiant) were employed as controls.

RESULTS

Ag and Sn cations released from the amalgams containing palladium were similar in concentration to those released from the commercial amalgams. The concentrations of released Cu and Hg cations decreased as a function of increased Pd concentration in the experimental amalgams. Averaging an order of magnitude of released Cu and Hg cations less than commercial controls for amalgam containing 1.7 w% Pd. Detection of Pd was essentially below the resolution of the technique and Zn was only detected in case of Dispersalloy.

CONCLUSIONS

Pd addition to high-copper amalgam alloy reduces the release of mercury and copper from the Pd-containing amalgam.

Adult presentation of congenital cystic adenomatoid malformation of the lung: a case report

Adult presentation of congenital cystic adenomatoid malformation(CCAM) of the lung is so rare that only 5 cases have been reported in the literature to date. We report the case of a 19-year-old female with CCAM in the left lower lobe. Computed tomography showed a multilobulated cystic lesion with multiple air-fluid levels and also showed focal enhancement of the solid component in the eccentrical portion of the lesion. Thoracic aortogram and selected bronchial arteriograms show a slightly enlarged and tortuous bronchial artery feeding the multilobulated cystic lesion. We present the clinical and radiological features of our case with a brief review of the literature.

Microleakage of endodontic temporary restorative materials

This study compared the sealing of Caviton, Cavit, and IRM at two powder to liquid ratios of 6 g/ml and 2 g/ml. Standard endodontic access preparations were made in 140 noncarious, nonrestored crowns of extracted human molars. They were divided into six groups, including positive and negative controls. Microleakage assessment was evaluated by basic fuchsin dye penetration after thermal cycling (5 to 55 degrees C for 100 cycles). The results indicated that Caviton provided the best seal, followed by Cavit. Cavit demonstrated better sealing than IRM at the powder to liquid ratio of 6 g/ml and 2 g/ml. There was a statistically significant difference in leakage between the Cavit group and IRM (powder to liquid = 6 g/ml), between the Cavit group and IRM (powder to liquid = 2 g/ml) group (p < 0.05). However, no statistically significant difference between the two different powder to liquid ratio groups of IRM was disclosed.

Shear bond strength of ceramic brackets with two bonding adhesives

The shear bond strength of two adhesives (Concise and Dyna-Plus bonding system) with one type of ceramic bracket was determined in this study. There were statistically significant differences between the bond strengths, with Concise recording higher levels than Dyna-Plus. Failure sites of Dyna-Plus were revealed at the enamel/resin, resin/resin, and resin/bracket interfaces; that of the Concise was mainly at the resin/bracket interface.

The properties of metal-reinforced glass ionomer materials

The physical properties and bond strengths of two glass ionomer materials reinforced with silver and amalgam alloy powders were compared with those of a conventional material from the same manufacture as well as two commercially available products. The diametral tensile strength, hardness and bonding strength are improved with the addition of either commercial available silver particles or fabricated high-copper amalgam alloy powders to the glass. Simple mixture of the metal or alloy powders with the glass ionomer cement seems to be feasible to improve the properties of the regular cement. However, further studies in formulating an optimal composition of metal or alloy, setting characteristics and long-term clinical evaluation are necessary before proposing uses for this new material.

Hydronephrosis secondary to congenital pelvic arteriovenous malformation: a case report

We report on a 26-year-old woman with a pelvic mass that caused ureteral obstruction and a hydronephrotic kidney. Diagnosis was congenital pelvic arteriovenous malformation and surgery was successful. The patient underwent staged preoperative intra-arterial embolization to decrease operative morbidity and facilitate complete removal.

The feasibility of castable ceramic material in dental bridge construction

This study was to investigate the feasibility of dental bridges constructed with castable ceramic material (Dicor). A dental bridge model was designed similar to the clinical situation. The marginal fit of Dicor crown and a three-unit bridge was evaluated and no statistically significant differences in marginal openings between Dicor crowns and bridges were determined except the mesial and distal end surfaces of the bridge works. The fracture strengths of different thicknesses of Dicor test bars were measured with a three-point bending technique in a jig mounted in a universal testing machine. The results revealed that the bridge design with the thickest (6mm) connector and the shortest (8 mm) width of the pontic had the highest fracture resistance. In addition, pores with size up to 50 microns were disclosed in the fractured interface. The optimal design of Dicor bridge is determined according to the results of this study along with the clinical trial.

Clinical use of single-dose surfactant TA therapy for premature infants with severe respiratory distress syndrome

A single dose of surfactant TA was given as rescue therapy to four small premature infants with severe respiratory distress syndrome requiring mechanical ventilation. Birth weights ranged from 810 to 1200 gm. The dose of 100-120 mg/kg was given at the mean age of 5 hours, with range of 3 to 7 hours. Following surfactant therapy, there was a significant improvement (p < 0.05) in a/APO2 (raising from 0.11 +/- 0.05 before treatment to 0.34 +/- 0.19 at 6 hours after treatment). There was also a significant reduction in the severity of respiratory distress syndrome at 24 hours post-therapy. One baby died of sepsis at 40 hours of life; one survived without complications. The other two cases developed severe bronchopulmonary dysplasia later. We concluded that early use of exogenous surfactant is beneficial in small premature infants with severe respiratory distress syndrome.

Characterization of a complementary DNA for rat liver aryl sulfotransferase IV and use in evaluating the hepatic gene transcript levels of rats at various stages of 2-acetylaminofluorene-induced hepatocarcinogenesis

A complementary DNA (cDNA) for rat hepatic aryl sulfotransferase IV (AST IV) was isolated, characterized, and used as a hybridization probe to evaluate the molecular basis for the differential expression of AST IV during 2-acetylaminofluorine (2AAF)-induced hepatocarcinogensis. The AST IV cDNA clone was obtained by immunochemical screening of a male Sprague-Dawley rat liver cDNA library. The AST IV cDNA was found to be 1.3 kilobases long and to encode a fusion protein which was reactive with an antibody to AST IV and enzymatically able to generate the sulfuric acid ester of N-hydroxy-2AAF. Sequence analysis of the AST IV cDNA showed it to be 1127 residues in length and to have essentially complete homology with PST-I cDNA, a previously reported (S. Ozawa, et al., Nucleic Acids Res., 18: 4001, 1990), 1028-base cDNA for an uncharacterized rat liver aryl sulfotransferase. Comparison of the PST-I/AST IV cDNA-deduced amino acid sequence with data from a partial (51%) amino acid sequence analysis of purified AST IV showed complete amino acid homology, confirming the identity of the cDNA and establishing that AST IV was an N-blocked, 291-amino acid protein with a molecular mass of 33,909 daltons. The AST IV cDNA sequence differed from the PST-I cDNA in two principal ways: the 5' end lacked 18 coding bases, and the 3' end contained a 190-base extention in the untranslated region, including a consensus sequence for signalling polyadenylation. Studies of AST IV gene transcript levels showed that the livers of rats fed 2AAF for 3 wk (early stage hepatocarcinogenesis) and hyperplastic nodules from the livers of rats fed 2AAF for 19 wk (intermediate stage hepatocarcinogenesis) displayed transcript levels similar to those of livers from normal rats. This contrasted with the 60 to 70% lower than normal capacity of the mRNA fractions to express AST IV observed during in vitro translation. These results indicated that modulation of AST IV expression at early and intermediate stages of hepatocarcinogenesis involved regulatory mechanisms at the translational level. In contrast, mRNA fractions isolated from some 2AAF-induced liver tumors or from known chemical carcinogen-derived rat hepatoma cell lines showed losses of both AST IV transcript level and in vitro translation capacity, suggesting that regulation at the transcriptional level may become important at late stages of 2AAF-induced hepatocarcinogenesis. These results indicated that the molecular mechanisms for the 2AAF-mediated down regulation of AST IV expression during 2AAF-induced hepatocarcinogenesis involved alterations in regulation at both translational and transcriptional levels.

Effects of posts on dentin stress distribution in pulpless teeth

A finite element analysis was carried out to study the roles of posts in reducing dentin stress in pulpless teeth. Two-dimensional plane strain models of the midlabiolingual section of a human maxillary central incisor were first analyzed. The results showed that the gold alloy post reduced maximal dentin stress by as much as 30%. However, the integrity of the dentin was compromised and the effects of the post were likely to be exaggerated in such models. In an effort to correct for these problems, plane stress models with side plates and axisymmetric models were analyzed. Posts were found to reduce maximal dentin stress by only 3% to 8% when the teeth were subjected to masticatory and traumatic loadings in these latter models. Although posts reduced maximal dentin stress by as much as 20% when the teeth were loaded vertically, teeth such as incisors and canines normally are not subjected to vertical loadings. Thus the reinforcement effects of posts seem to be doubtful in these teeth.