Study of gypsum-bonded casting investments. Part 2

The simultaneous differential thermal analysis--thermogravimetry (DTA-TG) method used in Part 1 of this two-part study was extended to analyse two gypsum-bonded dental casting investments, Kerr Cristobalite Inlay and GC Cristobalite Micro. Both investments had a similar cristobalite content of about 70 per cent. The remaining 30 per cent was dental stone in GCM, and a mixture of plaster and dental stone in KCl. Inclusion of plaster in KCl appeared responsible for the greater amount of water required for mixing this investment. The DTA-TG method used in the present study can be applied to identify the type and amount of hemihydrate, and the type of silica, in currently available gypsum-bonded investments.

Nicorandil as a nitrate, and cromakalim as a potassium channel opener, dilate isolated porcine large coronary arteries in an agonist-nonselective manner

Nicorandil is an antianginal vasodilator having a hybrid property between nitrates and potassium channel openers, and cromakalim is a relatively specific potassium channel opener. We investigated whether or not the vasorelaxant actions of the two drugs would be selective for certain vasoconstrictor agonists (simply agonists hereafter), and the underlying mechanisms in isolated porcine large coronary arteries. Both nicorandil and cromakalim produced a complete relaxation in the arteries precontracted with seven agonists, i.e., Bay-K-8644, endothelin, histamine, 5-hydroxytryptamine (5-HT), phenylephrine, PGF2 alpha, and U 46619. The EC50 values (-log M) of nicorandil and cromakalim were 5.20-5.44 and 6.43-6.87, respectively, toward the seven agonists, indicating that the vasorelaxant actions of the two drugs were agonist nonselective. In the arteries precontracted with Bay-K-8644, endothelin, 5-HT, and U 46619, the vasorelaxant action of cromakalim was antagonized by glibenclamide, an antagonist of potassium channel openers, and Schild analysis of these antagonisms yielded pA2 values of 7.10-7.41 for glibenclamide. The vasorelaxant actions of nicorandil in the arteries precontracted with the four agonists each were not antagonized by glibenclamide. Instead, the vasorelaxant action of nicorandil was antagonized by methylene blue (10 microM), an inhibitor of guanylate cyclase, and slightly potentiated by M&B 22,948 (10 microM), an inhibitor of cyclic-GMP phosphodiesterase, in the arteries precontracted with U 46619. These results indicate that the vasorelaxant actions of nicorandil and cromakalim in the porcine large coronary artery are agonist nonselective and that nicorandil exerts such an action entirely as a nitrate, whereas cromakalim does so entirely as a potassium channel opener.

FK-506: a new immunosuppressive agent, failed to reduce cerebral vasospasm after experimental subarachnoid hemorrhage

To define the relationship between the immunologic reaction and the pathogenesis of cerebral vasospasm (VS) following experimental subarachnoid hemorrhage (SAH), we examined the effect of a cell mediated immunosuppressive agent, FK-506, isolated from Streptomyces tsukubaensis, by using the canine SAH model. There was a significant vasoconstriction in the basilar artery in the control group after SAH. This constriction, however was not successfully prevented by FK-506 or combination of FK-506 and steroid, since there was no significant difference in the vessel caliber size among these groups. The pathologic approach, accompanied by immunohistochemistry, could not discriminate the differences in the nature of the lesion between the untreated group and FK-506 treated groups, except for slight lymphocytic infiltrations present around the basilar artery of untreated group. Histopathologically, inflammatory reactions consisting of neutrophils, that were not suppressed by FK-506 treatment, were clearly seen around the spastic vessels in the subarachnoid space. Furthermore, several constrictive changes or degenerative alterations were also observed in the spastic vascular wall. Immunohistochemically, the deposition of IgG, IgM and C3 was present in the intima and the luminal side of the smooth muscle layer, and capillary vessels of the brain stem. It is considered that this deposition was caused by increased vascular permeability in VS. On the basis of the above findings that the cell mediated immunosuppressive agent, FK-506 failed to prevent vasoconstriction or pathologic lesions but lymphocytic infiltrations, it is considered that the cell mediated immunopathogenesis may play little role in producing VS following SAH.

Correlation between E-cadherin expression and invasiveness in vitro in a human esophageal cancer cell line

E-cadherin, a member of the cadherin family, plays a major role in cell-cell adhesion of normal epithelium. Recent studies have shown that reduction or loss of E-cadherin expression in carcinomas have some relationship with their clinicopathological manifestation including invasion and metastasis. In the present study, we have established cell clones with different E-cadherin expression from human esophageal cancer, TE-2, and examined their adhesive capacity and invasiveness in vitro. Cell clones with positive E-cadherin expression [ECD(+) cells] were round and formed cobblestone colonies, while cell clones negative for E-cadherin [ECD(-) cells] had spindle shapes and formed dispersed colonies. ECD(+) cells showed higher adhesive capacity than ECD(-) cells, in both an aggregation assay with gyratory shaking culture and a dissociation assay of cells passing through the micropore membrane. Monoclonal antibody against human E-cadherin (HECD1) effectively diminished the mutual adhesion of ECD(+) cells but did not affect that of ECD(-) cells. Tumor invasiveness was evaluated with organotypic raft culture which is a coculture system consisting of two layers, a collagen gel layer containing fibroblasts and overlying reconstituted stratified squamous epithelium. ECD(+) cells formed complete stratified epithelium, but ECD(-) cells did not. ECD(+) cells did not invade the collagen/fibroblast gel, but ECD(-) cells did. Furthermore, ECD(+) cells showed invasion when an antibody against E-cadherin was used. Thus, loss or dysfunction of E-cadherin diminishes intercellular adhesion and results in the acquisition of invasive capacity in the cell line we examined.

Identification of novel members of G-protein coupled receptor superfamily expressed in bovine taste tissue

Using reverse transcription-polymerase chain reaction (RT-PCR) and degenerate oligonucleotide primers, we amplified novel members of two different subfamily of G-protein coupled receptor (GCR) superfamily from bovine taste tissue. Type A receptor clones composed of multiple cDNA clones had significant similarity with putative olfactory receptor subfamily, while a single type B clone had significant similarity with peptide receptor subfamily. Physiological functions of these receptors in taste cells are discussed.

Characterization of topa quinone cofactor

Electrochemical characterization of topa quinone (6-hydroxydopa quinone), the organic cofactor of copper-containing amine oxidases, has been performed with the aid of spectroscopy and ab initio energy minimization technique. Topa quinone exhibits a totally reversible cyclic voltammogram at a mercury electrode, which is ascribed to a two-step one-electron conversion between topa quinone and topa via topa semiquinone intermediate. Digital simulation of the reversible wave has afforded the separated estimation of each one-electron redox potential. The acid-dissociation constants of the phenolic hydroxyl groups of topa quinone, topa semiquinone and topa have been evaluated electrochemically and supported by electronic and electron spin resonance spectra. At pH 7.0, topa quinone is acid-dissociated and has a two-electron redox potential of 0.079 V vs. NHE coupled with a three-proton transfer. Redox catalytic activity of topa quinone for the oxidation of amines and NADH was not observed over conventional voltammetric time periods. Energy minimization calculation of acid-dissociated topa quinone anion indicates an intermediate electronic structure between the p- and o-quinone types with three almost equivalent carbonyl groups. The lack of the redox catalytic activity of free topa quinone appears to be attributable to the partial contribution of the p-quinone-type structure.

Orally active, nonpeptide vasopressin V1 antagonists. A novel series of 1-(1-substituted 4-piperidyl)-3,4-dihdyro-2(1H)-quinolinone

A series of compounds has been synthesized and demonstrated to be antagonists of V1 receptors both in vitro and in vivo. These compounds are structurally related to the 1-(4-piperidyl)-2(1H)-quinolinones, including OPC-21268, an orally bioavailable AVP V1 antagonist with high V1 specificity. It has been found that the introduction of an acetamide group on the terminal alkoxy chain of 41-44 leads to an increase in oral activity. Certain of these compounds may have efficacy in the study of AVP V1 receptors.

Induction of vascular endothelial tubular morphogenesis by human glioma cells. A model system for tumor angiogenesis

We have developed two different models of tumor angiogenesis by human brain tumors: one being tube formation by bovine aortic endothelial (BAE) cells cocultured with tumor cells in vitro, and other being in vivo angiogenesis in mice when tumor cells are transplanted into the dorsal sac. We investigated whether tube formation could be induced in BAE cells in type I collagen gel when these cells were cocultured with seven human glioma cell lines. Four of the seven glioma cell lines, which had high levels of basic fibroblast growth factor (bFGF) mRNA, induced tube formation by BAE cells. The tube formation was blocked by coadministration of anti-bFGF antibody. In in vivo model system of tumor angiogenesis in mice, these four cell lines were highly angiogenic. In contrast, with the other three glioma cell lines, which had poor expression of bFGF, BAE cells showed no apparent tube formation. These three cell lines did not efficiently develop capillary networks in mice. The results demonstrated a correlative relationship in the tubulogenesis of BAE cells, bFGF mRNA levels and angiogenesis in mice. The present study with two model systems of tumor angiogenesis suggests that the angiogenesis of some human glioma cell lines is mediated by bFGF, possibly via paracrine control.

[Usefulness of subtotal colectomy with colorectal anastomosis for chronic ulcerative colitis]

Recently in Japan, most of surgeons have been performing restorative proctocolectomy with ileoanal anastomosis for ulcerative colitis, leaving unsolved problems with regard to postoperative complications. Analysis was made on subtotal colectomy with colorectal anastomosis with the following policies. Firstly, the inflammation of the remnant intestine could be easily and correctly controlled by medication in outpatient. Secondly, carcinomas associated with ulcerative colitis can be discovered by postoperative colonoscopic examinations. Operations were carried out to 26 cases of ulcerative colitis for the past 13 years. Subtotal colectomy with colorectal anastomosis were performed to 11 cases. Three cases of colorectal carcinomas associated with ulcerative colitis were experienced. One of the resected specimen was investigated using stereomicroscopy after alcian blue staining to formalin fixed one. As a result of this research, we have convinced that colorectal anastomosis should be favorable surgical potion to the cases of chronic ulcerative colitis because postoperative anal function and quality of life are excellent in our series, in addition, carcinomas in the remnant intestine can be probably easily found out at the early stage by annual colonoscopic examinations with dye staining.

[Application of intravascular ultrasound imaging to carotid artery]

Although conventional angiography is utilized to assess the extent and severity of carotid artery disease, it yields only a silhouette of the vessel lumen. Intravascular ultrasound imaging (IUI), which has been developed for imaging the coronary artery, can supplement angiography by providing a tomographic perspective of the vessel wall structure. Therefore, we applied IUI (4.3F, 30MHz) to the carotid artery to evaluate the extent of arteriosclerosis, and we were successful in imaging the perspective of the carotid artery. Our results suggest that IUI is a useful device to evaluate the extent of atherosclerosis of the carotid artery.

Plasma brain natriuretic peptide level in pregnant women with pregnancy-induced hypertension

OBJECTIVE

To investigate the involvement of brain natriuretic peptide in the circulation of pregnant women with pregnancy-induced hypertension.

METHODS

We determined the plasma levels of brain and atrial natriuretic peptides in a cross-sectional study of 36 normal pregnant women and 17 women with pregnancy-induced hypertension.

RESULTS

During normal pregnancy, the plasma brain natriuretic peptide level was similar to that in nonpregnant women, but the plasma atrial natriuretic peptide level in the second trimester was significantly higher than that in nonpregnant women (P < .05). In women with severe pregnancy-induced hypertension, the plasma brain natriuretic peptide level was eight times higher than that in normal pregnant women in the third trimester; the plasma atrial natriuretic peptide level in the same patients was three times higher than that in normal pregnancy. The plasma brain natriuretic peptide level showed a positive correlation with the mean blood pressure (r = 0.62, P < .001).

CONCLUSION

The present findings suggest that brain natriuretic peptide is increased in the plasma of women with pregnancy-induced hypertension and that brain natriuretic peptide, in concert with atrial natriuretic peptide, participates in maintaining homeostasis of the maternal circulation.

Role of protein supplements in the culture of mouse embryos

The effect of various types of proteins used in single protein supplements for Bigger-Whitten-Whittingham (BWW) medium on the in vitro development of mouse preimplantation embryos was evaluated. Thioredoxin, superoxide dismutase (SOD), and apotransferrin showed prominent growth-promoting activity, whereas bovine serum albumin (BSA), fatty acid-free BSA, and catalase showed moderate promoting effects. beta-lipoprotein, ovalbumin and hemoglobin were ineffective, and holo-type transferrin and ceruloplasmin were actually toxic to the embryos. These results suggest that the growth-promotive effect of proteins on mouse pronuclear stage embryos is due to their antioxidative action, or to the removal of some free metal ion(s) such as Fe(3+). The mild growth promoting effect of both BSA and fatty acid free BSA suggest that the effect mediated by BSA is not dependent on bound fatty acids, but more likely is due to their antioxidative effect or chelating effect.

Effect of the rice bran-derived phytosterol cycloartenol ferulic acid ester on the central nervous system

In order to investigate the effect of cycloartenol ferulic acid ester (CFE, CAS 21238-33-5), a component of gamma-oryzanol which is a phytosterol derived from rice bran, on the central nervous system, a variety of pharmacological tests were performed. It was shown that CFE had a suppressant effect on the central nervous system, but its properties were different from those of existing major and minor tranquilizers. In addition, its efficacy in several models of cerebral dysfunction was demonstrated. Since any clear effects could not be obtained under the treatments with gamma-oryzanol, CFE seems to be more useful than gamma-oryzanol. Thus the results of this study suggest that CFE may serve as a new plant-derived cerebral activator possessing a wide range of pharmacological actions.

[Retreatment of pulmonary tuberculosis--duration of chemotherapy]

Although standard chemotherapy for initial treatment of pulmonary tuberculosis has been established, regimens for retreatment of tuberculosis have not yet been established. One hundred fifty nine retreatment pulmonary tuberculosis cases admitted to Fukujuji Hospital were retrospectively analyzed. Regardless of the age at the start of retreatment, majority of cases were treated previously between 1955 and 1960. Bacillary negative conversion rate, duration of chemotherapy, follow-up period and bacteriological relapse rate were compared according to resistance against isoniazid and/or rifampicin. Sixty four cases were sensitive to both INH and RFP. For this group the average duration of chemotherapy was 14.6 months, mean follow up period was 47.3 months and relapse rate was 3.1%. This rate was similar to that of initial treatment cases. Sixty one (94%), were treated with more than two sensitive drugs containing INH and RFP. The 22 INH-resistant and RFP-susceptible cases were treated for 18.6 months and followed up for 55.2 months. The relapse rate of this group was 13.6%. Thirteen cases were treated with more than 2 sensitive drugs containing RFP. Eleven cases were resistant to both INH and RFP. Five of them were surgically operated of which 3 cases were converted to negative and among the nonsurgical cases in this group only one remained sputum positive. All of these retreatment regimens did not contain pyrazinamide and ofloxacin. Although bacillary positive rate of INH and RFP susceptible cases was 13.0% at 6 months after treatment and 5.3% at 12 months after treatment, that of INH resistant and RFP susceptible cases were 25.0% and 12.5%, respectively. A certain rule of retreatment could be obtained from the result of this study.

3-Amino-1,4-dimethyl-5H-pyrido[4,3-b]indole (Trp-P-1) inhibits the removal of both cyclobutane dimers and (6-4) photoproducts from the DNA of ultraviolet-irradiated E. coli

Heterocyclic amines have been isolated from cooked foods and found to be mutagens and carcinogens. Among them, 3-amino-1,4-dimethyl-5H-pyrido[4,3-b]indole (Trp-P-1) and 3-amino-1-methyl-5H-pyrido[4,3-b]indole (Trp-P-2) were also found to enhance UV-induced mutation frequencies in Escherichia coli at the concentrations where they were neither toxic nor mutagenic by themselves. Using an immunological method recently developed to detect UV-induced DNA damage, we investigated the inhibitory effect of Trp-P-1 on the removal of both cyclobutane dimers and (6-4)photoproducts from the DNA of UV-irradiated E.coli. Cells repaired 60% of the initial cyclobutane dimers within 30 min and 75% at 120 min after UV-irradiation. Furthermore, the same cells repaired 90% of the initial (6-4)photoproducts within 30 min. On the other hand, Trp-P-1 clearly showed inhibition of repair of both photolesions in a concentration-dependent manner. The levels of repair inhibition by Trp-P-1 were almost the same between cyclobutane dimers and (6-4)photoproducts. These results suggested that the enhancing effect of Trp-P-1 on UV-induced mutagenesis in E.coli stemmed from the inhibition of the removal of photolesions from the DNA.

Immunohistochemical analysis of p53 protein over-expression in endometrial carcinomas: inverse correlation with sex steroid receptor status

Mutations of the tumour suppressor p53 gene have been reported in a variety of human malignant tumours, and are frequently associated with over-expression of p53 protein. To examine the significance of p53 gene alteration in endometrial carcinomas, we studied the immunohistochemical reactivity with a monoclonal antibody against p53 (PAb 1801) in 30 endometrial carcinomas as well as in 64 normal endometria. The presence or absence of correlation of p53 over-expression with the clinicopathological features and with the immunohistochemical expression of sex steroid receptors (oestrogen receptors; ER, progesterone receptors; PR) was also analysed. Expression of p53 was found in none of 64 normal endometria, but was identified in 5 of the 30 (16.7%) endometrial carcinomas. All 5 of the p53-positive tumours developed in women more than 3 years post-menopause, whereas the carcinomas in 5 pre-menopausal women and 3 women less than 3 years post-menopause were p53-negative. None of the 5 p53-positive carcinomas was associated with adjacent endometrial hyperplasia. Two of the 5 p53-positive tumours showed non-endometrioid histology: serous papillary and clear cell carcinomas. In contrast, 6 carcinomas accompanied by adjacent hyperplasia were p53-negative. In addition, ER and/or PR expression was found in none of the 5 p53-positive tumours, but was present in 21 of the 25 p53-negative tumours (p < 0.01). These clinicopathological features of p53-positive carcinomas and the inverse correlation of p53 immunoreactivity with sex steroid receptor status suggest that p53 over-expression is frequent in a specific category of endometrial carcinoma, presumably oestrogen-unrelated tumours.

Significance of p53 expression as a prognostic factor in oesophageal squamous cell carcinoma

The tumour suppressor gene product p53 is believed to play an important role in the progression of human malignant tumours through mutation and over-expression. Using a microwave oven heating method, we have detected over-expression of p53 in buffered-formalin fixed, paraffin-embedded sections of oesophageal carcinomas immunohistochemically and examined the relationship between the p53 over-expression and postoperative survival. Employing a monoclonal antibody (pAb1801), nuclear p53 was detected in 56 of 105 (53%) tumour specimens. Homogeneous, heterogeneous, and focal immunostaining patterns were noted. No immunostaining was found in adjacent benign tissues. The results in buffered-formalin fixed sections were similar to those in the frozen sections. The cumulative survival rate of patients with p53 expression was significantly lower than that of the patients without expression (P < 0.05), even though there were no significant differences between the clinicopathological features of the two groups. The results indicate that the nuclear accumulation of p53 might be an independent prognostic factor in patients with oesophageal squamous cell carcinomas.

The mechanism of hepatic cellular injury in sepsis: an in vitro study of the implications of cytokines and neutrophils in its pathogenesis

Neutrophil-mediated injury to hepatocytes was evaluated in vitro. A new in vitro coculture system of neutrophils and a human hepatoblastoma cell line (HuH-6), instead of normal hepatocytes, was established. Recombinant human tumor necrosis factor (TNF) activated neutrophils to release neutrophil elastase and showed the significant cytotoxicity for HuH-6 cells, which was determined by measuring the release of the cytoplasmic enzyme, lactate dehydrogenase (LDH), from HuH-6 cells. The concentration of neutrophil elastase from zymosan-primed/TNF (1.0 ng/ml)-stimulated neutrophils cocultured with HuH-6 cells reached to the level of 1.59 +/- 0.18 micrograms/10(6) cells in 24 hr. The release of LDH from HuH-6 cells in this coculture system was 84.8 +/- 17.8 units/liter after 24 hr incubation. Purified human neutrophil elastase also increased LDH release from HuH-6 cells. When HuH-6 cells were cocultured with zymosan-primed/TNF (1.0 ng/ml)-stimulated neutrophils, the secretion of the negative acute phase reactant (APR), alpha-fetoprotein, from HuH-6 cells was significantly decreased, and the production of the positive APR, pancreatic secretory trypsin inhibitor, was decreased in response to the stimulation of interleukin 6. Urinary trypsin inhibitor, the inhibitor of neutrophil elastase, decreased the release of LDH from HuH-6 cells cocultured with stimulated neutrophils, while superoxide scavenger did not. These results show that human neutrophils activated by TNF injure hepatocytes, thus causing hepatic dysfunction, through the release of neutrophil elastase.

Postoperative motor function and mucosal blood flow of lower esophagus: comparison between terminal esophagoproximal gastrectomy and esophageal transection for esophageal varices

Reflux esophagitis and anastomotic ulcer are potential complications associated with surgery for esophagogastric lesions. This study compared 10 cases following terminal esophagoproximal gastrectomy (TEPG) for esophageal varices and 20 cases following esophageal transection (ET) for esophageal varices with respect to postoperative motor function and mucosal blood supply, to ascertain the reason for the development of anastomotic ulcer. Endoscopic findings showed that anastomotic ulcers were detected more often after TEPG than after TR. Maximum swallowing pressure, high pressure zone pressure, and length did not differ between the two groups. However, maximum swallowing pressure in the lower esophagus after both procedures was significantly lower than in the control group (20 cases; p < 0.01). The results, measured by reflectance spectrophotometry, showed that the index of esophageal mucosal blood volume following TEPG is significantly lower than that following ET and in non-operated esophageal varices (10 cases; p < 0.01). Yet the index of oxygen saturation of hemoglobin was similar in the three groups. This study has demonstrated that patients undergoing TEPG have mucosal ischemia of the lower esophagus, causing the development of anastomotic ulcers.

Physicochemical properties of intermediary subunits of broad bean 11S globulin

Three intermediary subunits of legumin, IS-I, IS-II and IS-III, were isolated. They were characterized by means of electrophoresis, amino acid and NH2-terminal sequence analyses. Reconstitution of pseudolegumin was carried out and the yield of 11S-size product from either IS-II or IS-III was more than 95%, while IS-I almost formed a 9S-size product and a small amount of 11S-size product. The pseudolegumins were similar to the native legumin in terms of their secondary structure. The products from IS-I and IS-II formed a stronger gel than the native legumin upon heating, but that from IS-III failed to form a self-supporting gel. IS-I plays an important role in increasing the gel hardness of legumin.

Establishment of a human anaplastic thyroid cancer cell line secreting granulocyte colony-stimulating factor in response to cytokines

A human anaplastic thyroid cancer cell line K-119, derived from a 77-yr-old woman who had developed marked neutrophilia and underwent surgery for anaplastic thyroid cancer, has been established. The spindlelike and polygonal cells in shape are stably proliferating since the beginning of its culture 2 yr ago. The cells grow rapidly and the population doubling time is 26 h. The chromosomes show many abnormalities and many marker chromosomes have been observed. Heterotransplantation of the cells into nude mice has resulted in the formation of tumors that are histologically interpreted as anaplastic cancer. The most noteworthy characteristics of the cell line are the many Ki-67-positive cells (86.3%) and that the cell line spontaneously secretes granulocyte colony-stimulating factor (G-CSF) and releases increased amounts of G-CSF in response to the stimulation of tumor necrosis factor, interleukin 1 alpha, and interleukin 1 beta. The conditioned medium obtained from K-119 cells contains an autocrine factor stimulating the proliferation of themselves.

Increased generation of reactive oxygen species in embryos cultured in vitro

Previous studies have suggested that oxygen toxicity is closely related to the developmental blockage of embryos cultured in vitro. In this study, to obtain an actual proof of the increase in production of reactive oxygen species within embryos, we have measured the level of H2O2 in individual embryos using a fluorimetric method. Mouse (ICR) pronuclear stage embryos from the oviducts were cultured for a specified time under various conditions in a medium to which 2',7'-dichlorodihydrofluorescin diacetate was added. After washing the embryos, the fluorescence emissions of the H2O2-dependent oxidative product in embryos were measured. The fluorescent emissions were lowest in embryos cultured under 5% O2 and highest under 40% O2 (5% < 20% < 40%), just the inverse of the culture efficacy. The fluorescence emmissions of embryos cultured in Ham's F-10, which contains hypoxanthine and transition metals such as Cu and Fe, were higher than those cultured in BWW and alpha MEM, which do not contain these components (alpha MEM < BWW < Ham's F-10; again this is the inverse of the culture efficacy). The fluorescence emissions of embryos increased with the time of the exposure to visible light. L-cysteine and thioredoxin, both of which have been shown to promote embryo development, decreased the fluorescence emissions of embryos. All of these results would provide direct evidence for the hypothesis that oxygen radicals are involved in the developmental blockage.

Radiosensitization by a new potent nucleoside analog: 1-(1',3',4'-trihydroxy-2'-butoxy)methyl-2-nitroimidazole(RP-343)

PURPOSE

A new hypoxic cell sensitizer has been synthesized; this is a 2-nitroimidazole nucleoside analog having erythritol as a sugar moiety at the N-1 position of the imidazole ring (RP-343). Its possibility as a potent hypoxic cell sensitizer was compared with those of RP-170 and etanidazole.

METHODS AND MATERIALS

Radiosensitization was tested in two murine tumors, EMT6 using in vitro and in vivo-in vitro assays and SCCVII using growth delay and TCD50 assays. Pharmacokinetic study was performed in Balb/c mice bearing EMT6 tumors and in Beagle dogs. LD50 of each sensitizer was obtained with ICR mice.

RESULTS

As might be expected from the almost identical electron affinities of the three sensitizers, they were equally effective against hypoxic EMT6 cells in vitro. While having the lowest partition coefficient (0.035), RP-343 exhibited almost equally effective distribution to tumors and sensitizing radiation activity. An intravenous (i.v.) injection of 100 mg/kg of RP-343, RP-170 and etanidazole showed an almost equal sensitizer enhancement ratio (SER) of about 1.4 to solid EMT6 tumor under in vivo-in vitro assay and a virtually equal SER of 1.33-1.44 to solid SCCVII tumor under both tumor growth delay assay and TCD50 assay. A great advantage of RP-343 over RP-170 and etanidazole is its very much lower toxicity; their LD50 in mice were > 6.0, 4.3 and 4.8 g/kg, respectively, on i.v. injection. The lower toxicity of RP-343 was supported by its lower concentrations in the brain; the RP-343 AUC for brain was 0.43 times that of RP-170. Three indices were selected to compare the three nitroimidazoles. SER at 5% LD50 doses of RP-343, RP-170 and etanidazole was 1.66, 1.59 and 1.56. At the same toxicity levels, RP-343 was found to have better sensitization of solid tumors over both etanidazole and RP-170. The maximum tumor concentration/AUC for brain (Cmax,tumor/AUCbrain) ratios for RP-343 and RP-170 were 9.62 and 3.98.

CONCLUSIONS

This extremely high ratio of RP-343 could explain its lower toxicity than RP-170 or etanidazole. The therapeutic risk index defined as D1.5/LD50 (D1.5 is the sensitizer dose to obtain the SER of 1.5 in vivo) for RP-343, RP-170 and etanidazole were 0.022, 0.033 and 0.036, respectively. Especially, the effectively lower therapeutic risk index for RP-343 presents the possibility of clinical advantage over etanidazole.

Impaired growth hormone secretion in VMH lesioned rats

To investigate impaired growth hormone (GH) secretion in ventromedial nuclei (VMH) lesioned rats, we examined spontaneous plasma GH secretion, and plasma GH responses to arginine, clonidine and growth hormone releasing factor (GRF) under unanaesthetized and unrestrained conditions. Spontaneous GH secretion was blunted with 75% decrease of peak value in VMH lesioned rats, while it clearly existed in control rats. When rats were pre-treated with chlorpromazine (1-2 mg/kg, i.v.) which eliminates pulsatile GH secretion, no difference was observed in the plasma GH response to arginine (1 g/kg, i.v.) or to clonidine (100 micrograms/kg, i.v.) between VMH lesioned and control rats, but response to GRF (10 micrograms/kg, i.v.) was enhanced in the former animals. Administration of antiserum against somatostatin (1 ml) plus chlorpromazine significantly elevated the basal plasma GH level and GH response to arginine in control rats, but did not elevate them in VMH lesioned rats. These results suggest that reduction of both hypothalamic GRF and somatostatin release contribute to the impaired GH secretion in VMH lesioned rats. Reduction of somatostatin caused enhanced GH response to GRF and no increase in basal GH level with pre-treatment of antiserum against somatostatin. Reduction of GRF resulted in a failure to restore GH response to arginine with pre-treatment of antiserum against somatostatin. Reduction of both GRF and somatostatin caused blunted spontaneous GH secretion and normal GH response to arginine and clonidine.

Study of gypsum-bonded casting investments. Part 1

In order to develop analytical methods for identifying plaster or dental stone (calcium sulphate hemihydrate) and quantifying its content in gypsum-bonded dental casting investments, six dental gypsum products were studied by means of simultaneous differential thermal analysis-thermogravimetry (DTA-TG). Under the same analytical conditions employed in the present study, a phase change in calcium sulphate anhydrite (III-CaSO4 to II-CaSO4) was shown to occur at about 220 degrees C for four dental stones manufactured by various wet methods and at about 350 degrees C for two plasters manufactured by dry methods. This confirms the general view that the two types of calcium sulphate hemihydrate manufactured by dry or wet method could be identified by the DTA method. A reasonable estimate of chemically bound water could be made from the TG results at 300 degrees C. The present DTA-TG method can be used to identify the plaster or dental stone and calculate its content in gypsum-bonded casting investments.