Neutron radiography and other NDE tests of main rotor helicopter blades.

A few nondestructive examination (NDE) techniques are extensively being used worldwide to investigate aircraft structures for all types of defects. The detection of corrosion and delaminations, which are believed to be the major initiators of defects leading to aircraft structural failures, are addressed by various NDE techniques. In a combined investigation by means of visual inspection, X-ray radiography and shearography on helicopter main rotor blades, neutron radiography (NRad) at SAFARI-1 research reactor operated by Necsa, was performed to introduce this form of NDE testing to the South African aviation industry to be evaluated for applicability. The results of the shearography, visual inspection and NRad techniques are compared in this paper. The main features and advantages of neutron radiography, within the framework of these investigations, will be highlighted.

Glucagon stimulation test for the diagnosis of GH deficiency in adults.

The insulin tolerance test (ITT) is considered the test of choice for the diagnosis of GH deficiency (GHD). However, in patients with contraindications to ITT, alternative provocative tests must be used with appropriate cut-offs. The glucagon stimulation test has proved to be a safe, low-cost and effective means of stimulating GH secretion, and therefore can be considered as a suitable alternative to the ITT. We have studied the GH response to the glucagon test in 33 patients with known pituitary disease, 12 males and 21 females, aged between 21 and 60 yr (41.18 +/- 9.47 yr); 5 had isolated GHD and 28 had panhypopituitarism. We also evaluated a control group of 25 individuals, matched for age and sex (8 males and 17 females), aged between 20 and 60 yr (39.28 +/- 12.10 yr). They were selected via the ITT if their peak GH response was > 5.0 ng/ml. GH peak after glucagon was significantly lower in the group of patients compared to the control group (0.49 +/- 0.85 vs 8.69 +/- 5.85 ng/ml, p = 0.0001). Receiver-operating characteristic (ROC) plot analyses of the control and GHD group showed an area under the curve of 0.982 for GH peak response to glucagon. The response value of 3.0 ng/ml showed the best pair of sensitivity (97%)/specificity (88%), and was chosen as the cut-off defining GHD. After evaluation of positive predictive values (PPV) and negative predictive values (NPV) through simulation of different prevalences of the disease, we concluded that the cut-off point of 3.00 ng/ml maximizes both PPV and NPV (100%). In conclusion, we have shown that the glucagon stimulation test has a good performance and great diagnostic accuracy for the diagnosis of GHD.

Effect of experimental uremia upon the estrous cycle in rats.

By daily vaginal smears, uremic rats showed significantly greater prevalence of irregular estrous cycles compared with sham-operated controls (p less than 0.02). There seems to be a correlation between the degree of renal failure and estrous cycle abnormalities. The lack of LH surge on the afternoon of proestrus, found in uremic animals, suggests a defect in the positive hypothalamic steroid feedback.

A new plethysmograph for detecting arterial pulse waves in rat tail.

A new plethysmograph for detecting arterial pulse waves in the rat tail is described. With the objective of indirectly measuring the arterial blood pressure in small animal tails an easy-to-build plethysmographic chamber is presented. Essentially in this apparatus the atmospheric air insulated in the chamber is used as the transmitter of the volume changes caused by the arterial flow. By this methodology details of the pulse wave morphology are clearly visible, including the dicrotic notch. It is demonstrated that his chamber combines simplicity with accuracy.

Effect of experimentally induced renal failure upon the fertility in rats. Fertility in uremic rats.

Two groups of rats, one with surgically induced chronic renal failure and a sham-operated group were used. 10 weeks after surgery the animals were individually mated for 15 days according to 4 different schemes: uremic couple, control couple, a couple with a uremic male, and a couple with a uremic female. A second mating was allowed 18 weeks after surgery. There the uremic rats and nonfertile controls were matched against fertile controls. The experimental group showed a higher percentage of nonfertile rats, their offspring had fewer newborns and the uremic mothers had litters that weighed less at birth. In uremic males low plasma testosterone levels were detected. The analysis of plasma luteinizing hormone in the female and the delayed fertilization of uremic mothers suggest the presence of irregularities in the estrous cycle of uremic females.

Absence of zinc testicular deficiency in the sexual dysfunction of experimentally induced uremic rats.

Two groups of adult male rats were used. One group was sham-operated, while the other group had about 70-80% of the left kidney tissue surgically excised and a total right nephrectomy performed 10 days later. Two 15-day mating periods were organized at the 10th and 18th week after surgery. Fertile and infertile rats of the uremic group showed low testosterone levels and increased zinc content of testes in comparison to sham-operated animals. These data contrast with previous reports that zinc deficiency may be a cause of low testosterone values and sexual dysfunction in uremic patients. It is concluded that zinc deficiency may not be involved in the pathogenesis of low testosterone levels and sexual dysfunction in uremic male rats.

Effect of experimentally induced chronic renal failure upon the behavior of rats.

Two groups of rats were submitted to a 2-hour training session under a free operant avoidance of shock contingency 23 weeks after surgery, which provoked a state of chronic renal failure (experimental group) or after a sham operation (control group). Subjects in the control group had superior performances than those from the experimental group when total of shocks received and total numbers of avoidance and escape responses were compared. Results of biochemical blood analyses obtained from samples taken immediately after the avoidance training session indicate that the experimental group showed higher plasma urea concentration, higher levels of creatinine and osmolarity. The data show that the procedure used to provoke chronic renal failure was successful, and results in general confirm and extend findings relative to the effects of acute renal failure on behavior.

Effect of experimental chronic renal failure upon the production of urea, as measured by the liver arginase activity in rats.

A significant diminution in liver arginase activity of chronic renal failure uremic rats is described, thus implying that the experimental finding of an increased urea production is not due to a depressed arginase activity.

Renin production in Chagas' disease.

In six controls and ten patients with Chagas' disease (Trypanosomiasis cruzi), plasma renin activity was measured in peripheral venous blood, after 12 hours lying supine, and subsequently in an upright position at 5, 15, 30, 60 and 240 minutes. Evidence of a postganglionic autonomic defect at the sympathetic efferent kidney innervation was observed, probably in two stages corresponding to the clinical form of the disease: The first (asymptomatic or intermediate clinical form) with high renin production and the second with low renin production associated with digestive form of Chagas' disease.