Blackening of unprotected dental X-ray films due to scattered radiation

Abstract — Unexposed films awaiting exposure as well as exposed films awaiting processing are subjected to scattered radiation if kept unprotected in the dental X-ray clinic. The purpose of the present study was to analyze the influence of various storing principles, film speed, and distance from X-ray source upon the degree of film blackening. Test films were subjected to scattered radiation from 150 exposures. Maximum additional blackening (0.27 D) was recorded for type E films not protected by lead foil at the shortest distance studied (55 cm). As a distance of 200 cm blackening was reduced to 0.02 D and could be futher reduced by utilizing the inherent protective effect of the lead foil. It is concluded that if dental X-ray films not in use are kept at a distance of 200 cm from the X-ray source and protected by lead foil additional blackening due to scattered radiation is negligible and further protective precautions are unnecessary.     

Renal hypomagnesaemia in human diabetes mellitus: its relation to glucose homeostasis

Abstract. Interrelations between magnesium and glucose metabolism were studied in 215 insulin-treated diabetic out-patients aged 7–70 years. All had normal serum creatinine concentrations (below 115 μmol/l) and none had other diseases or received drugs known to interfere with mineral metabolism. A definite hypomagnesaemia (< normal mean —2 SD) and hypermagnesiuria (> normal mean + 2 SD) occurred in 38.6% and 55% of the patients. In the presence of hypermagnesiuria the serum magnesium concentration was inversely correlated to the urinary magnesium excretion rate ( R =–0.23, P <0.02). Serum magnesium correlated inversely with both fasting blood glucose ( R =—0.32, P <0.001) and the urinary glucose excretion rate ( R =–0.22, P <0.005). The urinary magnesium excretion rate correlated directly with the same variables ( R = 0.27, P <0.001 and R = 0.58, P <0.001, respectively). These data indicate that the net tubular reabsorption of magnesium is decreased in diabetic patients in presence of hyperglycaemia, leading to hypermagnesiuria and hypomagnesaemia.     

Afferent control of neuron numbers in the developing brain

In this study we tested whether the quantitative matching of developing neuronal populations may depend on the size of the afferent supply. Partial deafferentation of the middle division of the parabigeminal nucleus (PBm) was produced before the period of naturally occurring cell death, by reducing the neuronal population of the superior colliculus following partial lesions or eye removal. The number of neurons surviving cell death in the PBm was linearly related to the number of its afferent neurons. This result supports the hypothesis that neurotrophic control by the afferent supply during the period of natural neuronal death is a major determinant of the number of neurons in the developing brain.     

The HL-A7 Histocompatibility Antigen in Sarcoidosis Relation to Tuberculin Sensivity

Eighty cases of sarcoidosis have been investigated. In all except eight patients a histological verification of the diagnosis was obtained by mediastinoscopy or liver biopsy. The HL-A7 antigen was not increased in the entire group. However, in the group of patients with a negative sensitivity to tuberculin after the appearance of the disease there was a significant increase compared with controls. In the patients with a positive reaction, there was a complete absence of HL-A7. The HL-A system therefore does not seem to influence the liability to contract sarcoidosis, but once this condition has developed HL-A7 positives are more likely to lose cellular immunity to tuberculin and to reveal symptoms.     

Daily restricted feeding rescues a rhythm of period2 expression in the arrhythmic suprachiasmatic nucleus

Second only to light, daily restricted feeding schedules can entrain circadian rhythms in mammals [Neurosci Biobehav Rev 4 (1980) 119; J Biol Rhythms 17 (2002) 284]. Contrary to light, however, such feeding schedules have been found not to affect the master circadian clock in the suprachiasmatic nucleus (SCN) [Genes Dev 14 (2000) 2950; Eur J Neurosci 13 (2001) 1190]. Here, we show that in rats that are arrhythmic as a consequence of prolonged housing in constant light, a daily restricted feeding schedule not only restores behavioral rhythmicity, as previously shown [Physiol Behav 53 (1993) 509], but in addition, induces a rhythm of the clock protein, Period2 in the SCN. These findings challenge the idea that the SCN is invulnerable to feeding schedules and call for a reevaluation of the role of the SCN clock in the circadian effects of such schedules.