On the equivalence between homogeneously prepared sources and sources prepared by seeding in layers for different geometries, energies and matrix parameters

Measuring the radioactive content of environmental samples requires the use of appropriate reference materials with the same composition and density as the matrices to be measured. If they are not available, ad hoc artificially spiked reference materials are an alternative. Spiking in layers requires a detailed study of the drop distribution, as energy and decay scheme of the component radionuclides must be taken into account to produce a reference material that represents, in efficiency terms, a real sample. A method based on Monte Carlo simulation has been developed to find the optimal distribution of drops in layers for the combination of two typical soil samples and four radionuclides. Results have been validated by comparison with samples prepared by two techniques: methanol bath and spiking in layers.

Accreditation experience of radioisotope metrology laboratory of Argentina

This work presents the experience developed by the Radioisotope Metrology Laboratory (LMR), of the Argentine National Atomic Energy Commission (CNEA), as result of the accreditation process of the Quality System by ISO 17025 Standard. Considering the LMR as a calibration laboratory, services of secondary activity determinations and calibration of activimeters used in Nuclear Medicine were accredited. A peer review of the (alpha/beta)-gamma coincidence system was also carried out. This work shows in detail the structure of the quality system, the results of the accrediting audit and gives the number of non-conformities detected and of observations made which have all been resolved.

Short term effects of intra-arterial propionyl-L-carnitine on isolated canine hind-limbs

Treatment with propionyl-L-carnitine has been shown to increase the walking capacity of patients with peripheral vascular disease, but the mechanisms responsible for the effect are unknown. To study the effects of propionyl-L-carnitine on musculocutaneous vascular beds and the related mechanisms, a preparation of constant-pressure blood-perfused dog hind-limb was used. Since the propionyl-L-carnitine solution had a pH less than 4 the contralateral limb simultaneously received acidified saline. The substances were injected into the perfused arteries in 2 minutes or in 20 minutes, and the cumulative dose of propionyl-L-carnitine was 20 mg/kg for each administration. The preparation was well suited for this study, because there were no major systemic effects of propionyl-L-carnitine, nor signs of cross-circulation between the isolated limbs. Propionyl-L-carnitine increased flow by 130% in 2 minute infusions and by 49% in 20 minute infusions. Acidified saline increased flow by 47% in 2 minute infusions and by 34% in 20 minute infusions. The difference between propionyl-L-carnitine and acidified saline was significant in 2 minute infusions. The 2 minute infusions of propionyl-L-carnitine increased venous PO2 by 34% and PCO2 by 22% while pH decreased by 0.07. The 20 minute infusions of propionyl-L-carnitine increased PO2 by 22% and PCO2 by 24% while pH decreased 0.10 units. Acidified saline increased only venous PO2 in 2 minute infusions (16%). Calculated oxygen consumption of the perfused limbs increased in 2 minute infusions of propionyl-L-carnitine, but not significantly. It was concluded that propionyl-L-carnitine has a direct vasodilator effect in musculocutaneous vascular beds at high doses and probably enhances tissue metabolism.

Short-term hemodynamic effects of intravenous propionyl-L-carnitine in anesthetized dogs

The effects of intravenous administration of propionyl-L-carnitine (PLC) were investigated in anesthetized dogs instrumented for the analysis of general hemodynamic and electrocardiographic data, peripheral blood flows, coronary blood flow and oxygen consumption, urine flow, and renal function. PLC was administered in bolus (20, 60, and 200 mg/kg) or by infusion (20 mg/kg/min * 15 min or 30 mg/kg/min * 10 min). In some cases also L-carnitine (LC) and L-carnitine+propionate (LC + P) were administered in doses equimolar to those of PLC. PLC elicited dose-dependent, short-lasting enhancements of cardiac output, both in open- and closed-chest conditions. Arterial blood pressure, heart rate, and contractility varied slightly and unpredictably; the substance did not elicit electrocardiographic effects. These responses were not changed by alpha- or beta-adrenergic blockade, nor by the administration of a calcium antagonist, but they were abolished or reversed by the combination of such blocking interventions. Mesenteric and iliac blood flows were increased by both PLC and LC; LC + P increased these, and in addition increased renal blood flow. A strong diuresis obtained with PLC, LC, and LC + P was due to osmotic clearance following the administration of hyperosmotic solutions. PLC elicited coronary vasodilation with reduced oxygen extraction; this effect lasted longer than the general hemodynamic effects and was not seen with LC. All the cardiovascular actions of PLC can be attributed to its pharmacologic properties, rather than to its role as a metabolic intermediate.

A new 5-HT2 antagonist (ritanserin) in the treatment of chronic headache with depression. A double-blind study vs amitriptyline

The exact relationship between depression and chronic headache remains unclear. Considerable clinical and pharmacological evidence suggests the existence of a common biological terrain. Many antidepressant drugs are effective in the treatment of migraine and chronic headache disorders. Ritanserin, a new very selective serotonin-2 (5-HT2) antagonist, has recently shown both analgesic and antidepressant properties. The present study compares in a double-blind design, the effectiveness of ritanserin and amitriptyline, a well-known antidepressant extensively used in migraine prophylaxis. Thirty-eight patients (30 females and 8 males ranging in age from 20 to 50 yrs) were classified according to the International Headache Society criteria as: patients with chronic tension-type headache (CTH) (11 cases) and patients with coexisting migraine and CTH (MCTH) (27 cases). Only patients with a score equal to or higher than 18 on the Hamilton Rating Scale for Depression (HRSD) were included. Ritanserin was highly effective in reducing Pain Total Index and analgesic consumption in chronic headache, and its activity was similar to that observed during amitriptyline treatment. A significant improvement of HRSD and HRSA (Hamilton Rating Scale for Anxiety) scores was observed during both treatments. The main results of our study concern the demonstration of antiheadache and antidepressive properties of ritanserin. To better define the profile of the patients and their clinical responsiveness to the treatment, dexamethasone suppression test, clonidine test and nociceptive flexion reflex were investigated in our patients. Our data confirm the usefulness of these methods as markers of chronic headache with depression.

'Non-chronotropic' mechanisms on withdrawal of efferent vagal stimulation in anesthetized dogs

Withdrawal of the efferent vagal tone to the heart is an important factor of the increase of cardiac output (CO) and arterial blood pressure (ABP) in several conditions, such as exercise, emotion, postural changes. Vagal withdrawal enhances cardiovascular performance both by increasing heart rate (HR) and by other mechanisms, which were globally named 'non-chronotropic mechanisms'. The nature of these non-chronotropic mechanisms was studied in open-chest dogs under morphine-chloralose anesthesia. After cutting the cervical vagi and all the branches of the stellate ganglia except for the ansae subclaviae, the animals were prepared for recording HR, ABP, CO and left ventricular pressure (LVP). The experiments started during control vagal stimulations and consisted either in turning the vagal stimulators off (STOP), or in raising HR by atrial placing without withdrawing vagal stimulation (PACE), or in turning the vagal stimulators off while keeping HR constant by atrial pacing since the control vagal stimulation (STPA). Thus, STOP, PACE and STPA produced withdrawal of all vagal effects, of the chronotropic effects and of the non-chronotropic effects, respectively. Non-chronotropic mechanisms were evaluated both as the effects of STPA and as the difference between the effects of STOP and PACE. Experiments were repeated during stellate ganglion stimulation and during simultaneous atrio-ventricular pacing, to evaluate the role of vagosympathetic interactions and of atrial contractility. CO increased by 25% after STOP, by 20% after PACE and by 5% after STPA in the absence of sympathetic stimulation and by 30% after STOP, by 20% after PACE and by 10% after STPA during sympathetic stimulation. Stellate ganglion stimulation doubled non-chronotropic effects probably by potentiating vagal effects on myocardial contractility: after STPA the maximum LVdP/dt increased by 2% without sympathetic stimulation and by 7% with sympathetic stimulation. In all conditions, the increases in ABP after STOP, PACE and STPA were small and not statistically different between STOP and PACE. Simultaneous atrio-ventricular pacing in the absence of sympathetic stimulation nearly abolished non-chronotropic mechanisms, since CO increased to about the same extent both with STOP and with PACE. It is concluded that non-chronotropic mechanisms on vagal withdrawal consist mainly in the enhancement of atrial contractility and in the release of vagal restraint on the sympathetic effects upon the ventricles.

Interference of sympathetic innervation with reactive hyperemia in dog's skeletal muscle

The reactive hyperaemia (RH) after 30 sec arterial occlusion was studied in normal and chromically sympathectomized dog hindlimbs, under general chloralose anaesthesia. RH reached higher peak flow in the sympathectomized limbs, but the percent increase of flow was the same in both hindlimbs. The time course of RH was reduced in normal limbs, thus leading to a 35% decrease of the excess flow. The above results were explained on the basis of an economizing activity of the sympathetic basal tone on available oxygen due to effects on the microvasculature as well as on the cell metabolism. The autonomic tone is also responsible for steeper reduction of blood flow after RH in the normal limbs due to enhanced myogenic reaction.

The effect of the venom of Bitis gabonica on mesenteric and external iliac blood flow. - A preliminary study in the dog

The activity of the venom of Bitis Gabonica on mesenteric and external iliac circulation was investigated in four anaesthetized dogs. Venom doses of 0.125, 0.25 and 0.50 mg/kg were injected intravenously with an interval of 30 minutes between two successive injections. Following the first and the second dose, a transient fall of the resistance was observed in the mesenteric and especially in the external iliac vascular bed. Then, mesenteric resistance returned to normal, whereas external iliac resistance increased noticeable above the control value. After the third injection the animals died in a state of severe hypotension. It is note-worthy that during the transient vasodilation, mesenteric flow did not increase proportionally to the reduction of the relevant resistance, owing to the fact that BP fell more than would have been expected from the mesenteric vasodilation. This discrepancy seemed to depend on a more conspicuous reduction of the resistance in other vascular beds as observed in the external iliac circulation.

[Study of simple reaction time to lateralized visual stimuli]

Simple reaction time with manual response (right and left hand) to visual stimuli lateralized was studied in 20 normal subjects at 5, 20 and 35 degree in the nasal and temporal hemifields of the right eye. The reaction time was studied as a function of stimulus eccentricity. Uncrossed and crossed reaction times were examined with particular attention. No prevalence was found, neither of one hand, or of one hemisphere. The global speed of the two hemiretinas was the same, but reaction time increased as a function of stimulus eccentricity; moreover a better performance was obtained stimulating the nasal hemiretina at 35 degrees. Uncrossed reactions, considered on the whole, were faster than crossed ones (7,4 msec); the delay between crossed and uncrossed responses remained constant regardless of the degree of the visual stimuli eccentricity. The AA. concluded that such a difference is mainly dependent upon anatomical structures. The AA. also discuss several and often conflicting literature data and conclude that either the attentional model of the orienting responses as proposed by Kinsbourne, or the stimulus-response conpatibility effects, can be taken into consideration to explain some conflicting results; these results have been obtained by methods in some way different from those performed with present report (choice reaction times, absulute randomisation of the stimuli, response by crossed hands, choice verbal responses).

[Hemispheric specialization in recognition of alphabetic material]

Choice reaction time with manual response (right and left hand) to alphabetic stimuli (capital letters A-E = positive stimulus, and R-F = negative stimulus) projected at 5 degrees in the nasal and in temporal hemisfield of the right eye (half of the subjects) and of the left eye (the remaining half) was studied in 12 normal subjects (6 males and 6 females). The RT mean values were the result of the mean of the median of each block of trial, repeated in 4 sessions. The percentage of errors was also considered. The mean RT was calculated for each of the possible 4 experimental conditions hand-hemifield, in the males and females separately, and in all the cases. The data obtained, submitted to the statistical analysis, show a significant superiority of the left hemisphere in the recognition of the alphabetic stimuli, both in males and females, despite the prevalence of the right hand.

[Proline content of Italian wines (author's transl)]

Proline content of genuine wines from different areas is usually over 200 mg/1; a sample contained 1.920 mg/1; some samples has shown a lower content, with a minimum of 76 mg/1. No correlationship has been established between proline content and wine origin and age. Spectrophotometric method gives results markedly higher, in some cases, than give ion-exchange chromatogrpahy.