Regulation of nitric oxide synthesis by dimethylarginine dimethylaminohydrolase.

1. Dimethylarginine dimethylaminohydrolase (DDAH), an enzyme that metabolizes the endogenous nitric oxide synthase inhibitors NG-monomethyl-arginine and NG,NG-dimethy-L-arginine to citrulline, was identified by Western blotting in rat and human tissue homogenates. 2. S-2-amino-4(3-methylguanidino)butanoic acid (4124W) inhibited the metabolism of [14C]-NG-monomethyl-L-arginine to [14C]-citrulline by rat liver homogenates (IC50 416 +/- 66 microM; n = 9), human cultured endothelial cells (IC50 250 +/- 34 microM; n = 9) and isolated purified dimethylarginine dimethylaminohydrolase. 3. Addition of 4124W to culture medium increased the accumulation of endogenously-generated NG,NG-dimethy-L-arginine in the supernatant of human cultured endothelial cells from 3.1 +/- 0.3 to 5 +/- 0.7 microM (n = 15; P < 0.005). 4. 4124W (1 microM - 1 mM) had no direct effect on endothelial nitric oxide synthase activity but caused endothelium-dependent contraction of rat aortic rings (1 mM 4124W increased tone by 81.5 +/- 9.6% of that caused by phenylephrine 100 nM). This effect was reversed by L-arginine (100 microM). 4124W reversed endothelium-dependent relaxation of human saphenous vein (19.2 +/- 6.7% reversal of bradykinin-induced relaxation at 1 mM 4124W). 5. These data suggest that inhibition of dimethylarginine dimethylaminohydrolase increases the intracellular contraction of NG,NG-dimethyl-L-arginine sufficiently to inhibit nitric oxide synthesis. Inhibiting the activity of DDAH may provide an alternative mechanism for inhibition of nitric oxide synthases and changes in the activity of DDAH could contribute to pathophysiological alterations in NO generation.     

Bone loss of the radius in rheumatoid arthritis Comparison between 34 patients and 40 controls

We measured bone mineral density (BMD) in the radius by dual energy X-ray absorptiometry in 34 patients with rheumatoid arthritis (RA) and in 40 healthy controls. The BMD in RA patients in their fifties and sixties, but not in their forties and seventies, was significantly lower than that in the control subjects. The decrease in total radial BMD correlated with grip strength, RA activity and RA stage. The de crease in distal radial BMD correlated with RA activity, but not with grip strength. The levels of serum parathyroid hormone, alkaline phosphatase, and urinary hydroxyproline/creatinine were significantly higher in the patients. From these findings, we suggest that the bone loss in RA patients is affected by severity of inflammation, disuse, postmenopausal osteoporosis and secondary hyperparathyroidism.     

The further investigation on the gastric acid secretion in the primary hyperparathyroidism.

The gastric acid output was studied in the 11 patients of hyperparathyroidism before and after parathyroidectomy. The gastric acid output before operation was almost equal to the normal control in our hospital. After the correction of serum calcium by parathyroidectomy, the gastric acid output and serum gastrin were decreased. The decreased gastric acid output was recovered as the days passed since operation and approached to the preoperative level. The acid output in hyperparathyroidism was less in the case whose activity of alkaline phosphatase was more, which suggested that the calcium deposition on gastric mucosa might damage the parietal cell as the result of long lasting hypercalcemia.     

Correlation between expression of orotate phosphoribosyl transferase and 5-fluorouracil sensitivity, as measured by apoptosis index in colorectal cancer tissue

Background. 5-Fluorouracil remains a key drug in the treatment of colorectal cancer, and the development of a simple and effective test for selecting patients likely to benefit from postoperative adjuvant chemotherapy is an important objective. Aim of the Study. This study aimed to clarify the feasibility of measuring apoptotic cell rate (AI%) in tumor after short-term oral 5-fluorouracil administration prior to surgery with the objective of establishing a simpler method to test for sensitivity. Methods. Forty-five colorectal cancer patients were allocated to two groups, and 21 patients were given oral 5-FU for 3 d prior to surgery. The AI% in surgical specimen, detected by TUNEL staining, was compared in the 5-FU-loaded and control groups. The correlation of AI% with 5-FU metabolic enzyme mRNA levels in tumor was also evaluated. Results. The AI% was significantly higher in the tumor tissue of patients receiving 5-FU than in the control group (p<0.0005). Although insignificant, thymidylate synthase mRNA level and orotate phosphoribosyl transferase mRNA demonstrated a weak positive correlation with AI%. Conclusions. The AI% measurement in tumor tissue following a 5-FU oral load for 3 d prior to surgery was feasible. It remains to be elucidated if this measurement as a new 5-FU sensitivity test reflects the prognosis with 5-FU-based postoperative adjuvant chemotherapy.     

Heparin accelerates pulmonary artery development in neonate rabbits

Pulmonary vascular resistance drops sharply within a few minutes after birth for the survival of neonates. A majority of this resistance is caused by "pulmonary vascular bed" or vessel lacking smooth muscle cells. Heparin is known to promote proliferation and development of endothelial cells and to subsequently decrease their overall vascular resistance, but its detailed features remained unknown. Therefore, in this study we treated neonatal rabbits with heparin, protamine (antagonist of heparin), or saline, and evaluated histopathological features of vascular endothelial cells using two different types of computer assisted image analysis, i.e., CAS200 and NIH image. These two systems detected the percentage of vascular endothelial area per fields (VA) and CD31-positive area per total area of tissue following subtraction of background stain. CD31 was used as an endothelial cell marker. Heparin treated rabbits were associated with significant decrement of pulmonary/systemic artery pressure (Pp/Ps) (21.0 +/- 6.0%) compared to protamine (29.9 +/- 6.1%) or saline (29.4 +/- 3.0%) treated animals. The values of VA obtained by the two image analyses (CAS200 and NIH image) were significantly increased in heparin treated animals (38.4 +/- 3.2% determined by CAS200 and 24.0 +/- 1.3% by NIH image) compared to protamine (30.2 +/- 3.9% and 19.2 +/- 1.8%) or saline (33.2 +/- 1.5% and 20.8 +/- 3.8%) treated animals on 14th day of treatment. The present study indicates that heparin accelerates pulmonary vascular bed development probably by increasing the number and volume of endothelial cells, which subsequently contributes to the decrease in pulmonary vascular resistance.     

Optimization of tube potential-filter combinations for film-screen mammography: a contrast detail phantom study

This study evaluated how tube potential-filter combinations [with a molybdenum (Mo) anode and either an Mo or a rhodium (Rh) filter] influence image quality and radiation dose to breasts of different thicknesses in film-screen mammography using a new mammography phantom (CDMAM Phantom Type 3.4). A 28-kVp/Mo tube potential-filter combination is recommended for a breast (phantom) thickness of 40 mm or less, 28 kVp/Rh for a breast (phantom) thickness of 60 mm or less, and 30 kVp/Rh for a breast (phantom) thickness greater than 60 mm.     

Effect of maternal exposure to tributyltin on reproduction of the pearl oyster (Pinctada fucata martensii)

We examined the effect of tributyltin (TBT) on reproduction of the pearl oyster (Pinctada fucata martensii). In a maternal exposure test, five female pearl oysters were exposed to TBT at measured concentrations of 0 (control), 0.092, or 0.191 microg/L at 25 degreesC for one week, and the embryo developmental success (the ratio of normal D-larvae to all larvae) was measured. The embryo developmental success was significantly decreased in the 0.191-microg/L treatment group (65.5%) compared to that in the control group (82.5%; p = 0.031). Concentrations of TBT in the ovary reached 0.088 microg/g in the 0.191-microg/L treatment group. In a waterborne exposure test, inseminated eggs were exposed to TBT at measured concentrations of 0 (control), 0.020, 0.045, 0.091, 0.192, or 0.374 microg/L for 24 h. The embryo developmental success also was significantly decreased in the 0.192-microg/L treatment group (78.3%; p = 0.020) and no development at all was observed in the 0.374-microg/L treatment group compared with that in the control group (95.4%). These results clearly demonstrate that TBT accumulating in the bodies of bivalves has the potential to inhibit reproduction.     

No clinical correlation between bilirubin levels and severity of retinopathy of prematurity

PURPOSE: To evaluate the hypothesis that bilirubin has a protective effect against the development of severe retinopathy of prematurity (ROP). METHODS: An assessment of 76 infants born at 24 and 25 weeks' gestation and admitted to the level III neonatal intensive care unit at Saitama Children's Medical Center was made. Indirect ophthalmoscopy fundus examinations were performed on all infants to identify the degree and progression to threshold ROP. We analyzed the daily bilirubin levels and grouped the patients according to the severity of ROP based on the infant's worst ROP examination. The first group was comprised of infants with less than stage 3 ROP and infants with stage 3 ROP. The second group was infants with less than prethreshold ROP or prethreshold ROP, and infants with threshold ROP. Next, we divided the infants into 3 groups: less than prethreshold ROP, prethreshold ROP, and threshold ROP. The daily changes in serum bilirubin concentrations during the first 14 days of life were determined for each infant. Three groups (less than prethreshold ROP, prethreshold ROP, and threshold ROP) were comparable as to their basic data, clinical characteristics, and treatments. RESULTS: ROP was found in 76 infants. There were no statistical differences in the clinical characteristics and treatments, excluding the duration of phototherapy, among the 3 groups. During the first 14 days of age, there were no significant differences in the daily mean bilirubin concentrations according to the groups separated by severity of ROP. CONCLUSION: These results indicate that there is no distinct protective effect of bilirubin on the development of severe ROP.