Uncertainty studies of topographical measurements on steel surface corrosion by 3D scanning electron microscopy.

Pitting corrosion is a damage mechanism quite serious and dangerous in both carbon steel boiler tubes for power plants which are vital to most industries and stainless steels for orthopedic human implants whose demand, due to the increase of life expectation and rate of traffic accidents, has sharply increased. Reliable methods to characterize this kind of damage are becoming increasingly necessary, when trying to evaluate the advance of damage and to establish the best procedures for component inspection in order to determine remaining lives and failure mitigation. A study about the uncertainties on the topographies of corrosion pits from 3D SEM images, obtained at low magnifications (where errors are greater) and different stage tilt angles were carried out using an in-house software previously developed. Additionally, measurements of pit depths on biomaterial surfaces, subjected to two different surface treatments on stainless steels, were carried out. The different depth distributions observed were in agreement with electrochemical measurements.

FERImage: an interactive program for fractal dimension, d(per) and d(min) calculation.

A computer program has been written for the determination of the D fractal dimension at low scale, of the d(per) representative parameter of the periodical region at high scale, and the d(min), representative parameter of the minimum elemental cell which is repeated in the periodical structure from the variogram. It carries out the simultaneous obtention of the three previous parameters developed by Bonetto and Ladaga. The program also allows to obtain fractal dimension values from the Fourier power spectrum. FERImage has been developed so that the users could choose the rank where the behavior is fractal, not only in the variogram method but also in the Fourier spectrum method.

Purification of glomerulopressin.

The present investigation was undertaken to attempt the purification of glomerulopressin. Isolated rat livers were perfused with Krebs-Ringer bicarbonate, and the perfusate was concentrated at reduced pressure, extracted with n-butanol, and subjected to thin-layer chromatography (TLC) with different solvent systems. For monodimensional TLC, (a) acetic acid or (b) chloroform/methanol/formic acid (65:30:5, v/v) was used. For bidimensional TLC solvent (b) was used as the first mobile phase and as the second mobile phase three different solvent systems were employed as follows: ethyl acetate/n-butanol/formic acid (40:57:3; v/v), pyridine/methanol/formic acid (50:49:1, v/v), and acetic acid/n-butanol/water (5:50:10, v/v). The activity of the spots viewed under uv light was studied in three different biological assays: increase of the glomerular pressure index (GPI) in the toad and of the glomerular filtration rate (GFR) in the rat and increase of the tonic tension contraction in the rat stomach strip (TTC). In monodimensional TLC developed with system (a), three spots were detected, and with system (b), seven spots were observed. The biological activity of these seven spots was studied. Only the substance showing Rf 0.47 was active. This Rf 0.47 spot subjected to bidimensional TLC with the three different solvent systems moved in the second direction as only one spot. To confirm whether the Rf 0.47 spot was composed by only one substance, reverse-phase HPLC was performed in a Waters radial compression unit using three different elution systems and in a Hewlett-Packard model equipped with an ultrasphere ODS column. With these different HPLC columns and elution systems, only one peak was observed. This is the first attempt to purify a substance showing a biological activity similar to that of glomerulopressin.

Effect of glomerulopressin on several isolated veins and arteries of different species.

The effect of glomerulopressin was investigated in several isolated veins and arteries of dog and also in veins of rabbit, rat, and hamster. Glomerulopressin contracted some of the dog veins: jugular, extrahepatic porta, femoral, cava, iliac, splenic, and had no effect in pulmonary, mesenteric, and renal vein. It was also active in some dog arteries: Iliac, femoral, renal, and had no effect in aorta, hepatic, splenic and pulmonary artery. In the rat it increased the frequency of the spontaneous rhythmic contraction of the extrahepatic porta. No effect was observed in any of the rabbit veins assayed: cava, jugular, iliac and extrahepatic porta, nor in the extrahepatic portal vein of the hamster. In another group of experiments, inhibitors of phospholipase A2, chlorpromazine and mepacrine were added to the bath. These inhibitors blocked the effect of glomerulopressin in the three dog vessels that were assayed: jugular, extrahepatic porta and iliac artery. These results show that glomerulopressin induces a contraction in several, but not all, veins and arteries, and that its effect is mediated by the liberation of arachidonic acid.

Glomerulopressin activity in peripheral blood of newly diagnosed type I (insulin-dependent) diabetic patients and in normal subjects treated with glucagon.

The glomerulopressin activity of the ultrafiltrate obtained from the peripheral blood of normal subjects, newly diagnosed Type I (insulin-dependent) diabetic patients (IDD), and in normal subjects treated with glucagon was studied in two bioassays: tonic tension contraction of the rat stomach fundus (TTC) and increase in the ureteral pressure of the toad, which was considered as a glomerular pressure index (delta GPI). The ultrafiltrate of four normal volunteers had a low activity in the TTC assay, and in two subjects no activity was observed. The ultrafiltrate of five of these subjects had no activity in delta GPI. In IDD patients the ultrafiltrates were active in the TTC assay and in the toad assay. In glucagon treated normal volunteers three of the ultrafiltrates were very active in the TTC assay and other three had a low activity. In the toad assay five of them were active and no response was observed in one subject. These observations suggest that glomerulopressin activity is increased in peripheral venous blood of untreated newly diagnosed IDD patients and in normal subjects treated with glucagon.

Isolated dog coronary arteries response to glomerulopressin.

Coronary arteries were excised from pentobarbital anesthetized normal dogs. The isolated coronary arteries were placed in an oxigenated KRB bathing solution maintained at 37 degrees C and pH 7.4 changes in the basal tone were measured. The addition of glomerulopressin to the bathing solution produced a decrease of 26 +/- 1.5 mg of the basal tone. This decrease was prolonged for more than 40 minutes. Several inhibitors of prostaglandins synthesis were added to the bath such as corticosterone (2 X 10(-5) M), indomethacin (6 X 10(-6) M), acetylsalicylic acid (1.8 X 10(-4) M) and tranylcypromine (4 X 10(-4) M). All these inhibitors blocked the action of glomerulopressin. We conclude that glomerulopressin relaxes the coronary arteries and that this relaxation may be mediated through the novobiosynthesis of prostaglandins.

Induction of glomerulopressin production by cyclic AMP.

Isolated rat livers were perfused with gassed Krebs-Ringer-Bicarbonate and different doses of theophylline and dibutyryl cyclic AMP were added to the perfusing solution. The perfusates were ultrafiltrated through Diaflo UM-05 membranes. The glomerulopressin activity of the ultrafiltrates were assayed in the tonic tension contraction (TTC) of isolated stomach fundus from rats. As glomerulopressin is known to be a glucuronide, it was inactivated with beta-glucuronidase to confirm that the effect on the stomach fundus was due to the glomerulopressin and not to another substance. It was observed that doses of theophylline between 2 x 10(-3) M and 2 x 10(-5) M enhanced glomerulopressin production. However, there was no relationship between dose of theophylline and the response, and a dose of theophylline 2 x 10(-6) M has no activity. The perfusion with dibutyryl cyclic AMP at 5 x 10(-8) M increased the amount of glomerulopressin produced by the liver. This was a log-dose response of glomerulopressin production to dibutyryl cyclic AMP between 5 x 10(-8) M and 5 x 10(-4) M. Theophylline (2 x 10(-6) M) potentiated the activity of cyclic AMP (5 x 10(-8) M). These results support the view that cyclic AMP is intracellular mediator of the hepatic production of glomerulopressin.

Influence of insulin and glucagon on the production of glomerulopressin by isolated rat liver.

Isolated rats livers were perfused with Krebs-Ringer-Bicarbonate (KRB) and different doses of insulin or glucagon and with insulin plus glucagon. The isolated liver of fasted rats and of rats treated with streptozotocin were perfused with (KRB). The glomerulopressin activity of the ultrafiltrate of the liver perfusates were assayed in the tonic tension contraction (TTC) of isolated stomach fundus from rats. As glomerulopressin is known to be a glucuronide, it was inactivated with beta-glucuronidase to confirm that the effect on the stomach fundus was due to the glomerulopressin and not to an autacoid. It was observed that glucagon increased the glomerulopressin activity of the perfusate and that this activity was independent of the dose of glucagon used. Insulin produced a decrease in the glomerulopressin activity of the perfusate, there being a log-dose relationship between insulin and glomerulopressin. There is a dose of insulin (1,5 X 10(-5) U/min/kg) that potentiates the response to glucagon. Fasting and treatment with streptozotocin induced an increase in the glomerulopressin activity of the perfusate. These results suggest that glomerulopressin production is influenced by glucagon and insulin, and that there is a specific ratio between these hormones that is very effective in the production of glomerulopressin.

Influence of corticoids on the production of glomerulopressin by isolated rat liver.

The isolated liver of rats treated with dexamethasone, hydrocortisone, and deoxycorticosterone acetate (DOCA) was perfused with Krebs-Ringer Bicarbonate (KRB). The liver of adrenalectomized rats was also perfused with KRB. The glomerulopressin activity of the ultrafiltrate of the liver perfusates was assayed in the tonic tension contraction (TTC) of isolated stomach fundus from rats. As glomerulopressin is known to be a glucuronide, it was inactivated with beta-glucuronidase to confirm that the effect on the stomach fundus was due to the glomerulopressin and not to an autacoid. It was observed that dexamethasone, hydrocortisone and DOCA inhibit glomerulopressin production, but adrenalectomy had no effect, therefore it can be deduced that the adrenals are not necessary for the production of glomerulopressin.