Cerebral Blood Flow during Experimental Hypoxaemia and lschaemia in the Newborn Piglet

Odden, J.-P., Stiris, T., Hansen, T. W. R. and Bratlid, D. (Neonatal Research Laboratory, Department of Paediatric Research, Institute for Surgical Research and Department of Paediatrics, Rikshospitalet, University of Oslo, Oslo, Norway). Cerebral blood flow during experimental hypoxaemia and ischaemia in the newborn piglet. Acta Paediatr Scand Suppl 360: 13, 1989.
The effect of selective hypoxaemia or ischaemia on cerebral blood flow was studied in 14 newborn piglets with the microsphere method. Surgery and experiments were performed under general anesthesia with 70% nitrous oxide. The spontaneously breathing piglet was then exposed to either low (zero) oxygen in the inspired air (hypoxaemia), or a graded tourniquet (3–5 kg string weight) of the neck above the level of the tracheostomy (ischaemia). Cerebral blood flow was measured at baseline, during the hypoxaemic/ischaemic insult, and 30 and 60 min thereafter. Brainstem blood flow was remarkably stable during both ischaemia and hypoxaemia. The reduction in blood flow to the cerebrum and to the cerebellum was greater during ischaemia than during hypoxaemia. Reactive hyperaemia followed hypoxaemia but was not obvious after selective ischaemia. Ischaemia and hypoxaemia thus seem to have different effects on cerebral blood flow.     

Mercury vapor levels in a dental laboratory

abstract — Mercury vapor levels associated with grinding amalgam models and mulling amalgams in the palm of the hand following trituration have been measured in a dental laboratory in inhalation position. The threshold limit value of airborne mercury of 0.05 mg/m³ was essentially exceeded in the grinding procedure of amalgam. Levels in excess of seven times this value were recorded. During mulling the mercury vapor level fluctuated around the threshold limit value. The mean mercury concentrations did not essentially exceed the threshold limit value.     

Glycolate Causes the Acidosis in Ethylene Glycol Poisoning and is Effectively Removed by Hemodialysis

Abstract Six male patients with severe ethylene glycol poisoning were studied with respect to the origin of the metabolic acidosis. The plasma concentrations of ethylene glycol were 4–41 mmol/l and treatment included alkali, ethanol and hemodialysis. Plasma analysis by isotachophoresis and whole blood lactate determinations showed that glycolate (17.0–29.3 mmol/l), lactate (1.4–6.2 mmol/l) and β-hydroxybutyrate (≤1.8 mmol/l) were present in elevated concentrations contributing to the acidosis. Oxalate (≤0.33 mmol/l), glyoxylate (<0.2 mmol/l) and formate (<0.4 mmol/l) concentrations were negligible and did not contribute to any significant degree to the acidosis. The elevated plasma glycolate concentration was highly correlated to the anion gap (r=0.923) and the glycolate made up for 96.1% (n=6, range 84.7–108.8) of the increased anion gap. We conclude that glycolate accumulation is the main reason for the metabolic acidosis in ethylene glycol poisoning. The mean dialysator (1.6 m²) clearances of glycolate at a blood flow of 200 ml/min in two patients were 137 ml/min (n=9, SD±8, range 125–149) and 144 ml/min (n=11, SD±8, range 133–158). By applying first order kinetics during hemodialysis a volume of distribution of glycolate of 0.55 l/kg was found, assuming that the dialysator clearance equals the total body clearance of glycolate. Thus glycolate, the probable main metabolite of ethylene glycol, is efficiently removed by hemodialysis.     

Gastrointestinal and in vitro release of copper, cadmium, indium, mercury and zinc from conventional and copper-rich amalgams

Abstract – Particles of a conventional lathe-cut, a spherical non-gamma 2 and a copper amalgam have been gastrointestinally administered to rats for the purpose of evaluation of the dissolution resistance. The animals were sacrificed after 20 hrs. The contents of copper, cadmium, indium, mercury and zinc in kidney, liver, lung or blood were measured using nuclear tracer techniques. From a copper amalgam an extreme release of copper was demonstrated. This study simulates the clinical condition of elemental release from swallowed amalgam particles after amalgam insertion or after removal of old amalgam fillings. Specimens of the same types of amalgams were also exposed to artificial saliva for a period of 10 days. The amounts of copper and mercury released were measured with flame and flameless atomic absorption spectrophotometry respectively. The levels of copper and mercury released from the copper amalgam were approximately 50 times those of the two other amalgam types studied.     

Elements in minor or trace quantities in zinc phosphate cements

Abstract – Eight powders and two liquids of zinc phosphate cements have been analyzed by optical emission spectrography for the purpose of characterizing elements in minor or trace quantities. The following elements were measured: bismuth, boron, cadmium, chromium, copper, iron, lead, silver and titanium. The content of any of these elements did not exceed the level of 0.1%. The amounts of such elements which might be transferred to the gastrointestinal tract associated with dissolution from unsuccessful restorations have been considered.     

Levels of airborne particles resulting from handling alginate impression material

ABSTRACT – The levels of airborne particles emanating from handling alginate impression powders have been surveyed. The concentrations of powders, lead and silicious particles in the aerosol have been measured after thoroughly shaking the containers before opening. The decrease of the powder concentration in the ambient air as a function of time has been estimated. The efficiency of face masks to protect against powder exposure has been investigated.     

Exposure to mercury and silver during removal of amalgam restorations

The content of particulate matter and mercury vapor in dentist breathing air during removal of amalgam restorations was assessed. Mercury and silver were quantitatively assayed by nuclear chemical analysis, and the mercury vapor concentration was measured with a sniffer. When the water spray was not used, the short time threshold limit values for exposure to mercury and silver were exceeded about 10 times. With water spray the mercury content was reduced to a level considerably lower than the threshold limit value, whereas the silver concentration slightly exceeded the corresponding limit.     

The effect of REM sleep deprivation on somatostatin and growth hormone-releasing hormone gene expression in the rat hypothalamus

Growth hormone-releasing hormone (GHRH) and somatostatin (SRIF) have been implicated as sleep factors. We studied how the hypothalamic SRIF/GHRH system is affected by possible feedback regulation resulting from REM sleep deprivation at the level of gene expression and how this is reflected in serum growth hormone (GH) content. Male rats were deprived of REM sleep on small platforms for 24 or 72 h, and one group was allowed a rebound sleep of 24 h after 72 h deprivation. Animals maintained on large platforms and animals taken directly from their home cages served as controls. In situ hybridization was made from 20 μm cryosections through the periventricular, paraventricular and arcuate hypothalamic nuclei using oligonucleotide probes for GHRH and SRIF. The number of cells expressing SRIF or GHRH was counted. Serum GH was measured by means of radioimmunoassay in similarly treated rats. Fewer cells expressed GHRH in the paraventricular nucleus of animals subjected to 24 and 72 h of REM sleep deprivation than in home control animals. A similar trend was observed in the arcuate nucleus. The number of cells expressing SRIF was elevated in the arcuate nucleus after 24 h of REM sleep deprivation but not after 72 h. In the periventricular nucleus the number of cells expressing SRIF was higher after 72 h of deprivation when compared to expression in animals maintained on large platforms. Serum GH levels were decreased in animals maintained on either small or large platforms. It is concluded that the expression of the SRIF and GHRH genes is modulated by REM sleep deprivation.     

Influence of antiseptic storage solutions on physical properties of endodontic guttapercha points

The effect of three commonly used antiseptic storage solutions on some physical properties of endodontic guttapercha points was studied. The solutions tested were: 70% isopropyl alcohol, 5% chloramine and 0.5% chlorhexidine. As a control solution, physiologic saline was used. There was a marked decrease in the force necessary to bend the points after 1 month. With few exceptions, the greatest decrease was seen with solutions containing alcohol, i.e. chlorhexidine and isopropyl alcohol. The difference between aqueous and alcoholic storage solutions was also noted for linear dimensional changes. Physiologic saline and chloramine hardly affected the length of the points. The decrease in stiffness may add to the difficulties when handling guttapercha points of small dimensions in curved root canals. From this point of view it is therefore recommended to avoid storage of points in antibacterial solutions. Rather, an effective surface disinfecting of the points immediately prior to use would be desirable.