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A system for calibrating and using a group of dc and ac standards has been developed at NBS to meet increasing needs for greater accuracy in the measurement of direct and rms alternating voltages at audio frequencies. With a group of saturated cells, a universal ratio set as a potentiometer, a simplified self-calibrating volt box, and a new differential-thermocouple ac-dc comparator, an accuracy of 10 ppm can be obtained for direct voltage measurements and 40 ppm for rms alternating voltage measurements between 20 and 20 000 c/s, in terms of the direct volt and the ac-dc transfer standards maintained at NBS.

The ac-dc differences of a reference group of thermoelements have been evaluated at audio frequencies to a few parts per million (ppm) at currents from 5 to 20 mA. A technique for comparing the ac-dc differences of two thermoelements with an uncertainty of about 2 ppm has been developed. Two 5 mA thermoelements are used with a plug-in set of resistors of computable reactances to form thermal voltage converters for voltage measurements. With this same technique adjacent ranges of these converters can be compared to step up from 0.5 to 500 V to better than 10 ppm.

Thyroxine-binding globulin (TBG) levels were found to be significantly lower in 40 thyrotoxic patients than in 70 healthy subjects. A similar mean fall in TBG of 18% was produced by administration of 'physiological' doses of triiodothyronine to healthy volunteers. However, intramuscular injection of thyroid-stimulating hormone (TSH) had no consistent effect on the level of TBG as measured up to 4 days after injection. These findings are believed to explain the anomalous results described by earlier workers. It is suggested that TBG concentration is regulated by unknown mechanisms subject to the influence of many hormones, including triiodothyronine.

(1932). The Moslems in Tunisia. Journal of The Royal Central Asian Society: Vol. 19, No. 4, pp. 653-666.

Directional counters and the methods of increasing their efficiency are briefly reviewed. A simple Perspex conical crystal holder is described. This acts as a reflector, provides an airtight mounting for hygroscopic crystals, and allows a narrow aperture detector to utilise the full photocathode surface. Calcium tungstate and thallium-activated sodium iodide crystals are compared when used with such a holder. The detection efficiency of the apparatus as a whole was increased in both cases.

Thermal voltage converters, each consisting of a resistor in series with a thermoelement in a coaxial line, have been developed for measurements of rms voltages of 1 to 200 volts at frequencies from 3 cps (cycles per second) to 30 mc (megacycles). An accuracy of 0.1% or better may be obtained by a-c-d-c transfer techniques up to at least 10 mc and 0.2% at 30 mc.

1. Specific radioimmunoassays have been employed to measure triiodothyronine (T3), and thyroxine (T4) concentrations in the cord serum of fifty-five healthy babies and in a second series of fifteen paired cord and maternal blood samples. 2. The mean cord serum T3 was 332±136 (SD) pg/ml. In the paired series the mean cord serum T3 was 355±142 pg/ml whereas the mean maternal value was 1557±283 pg/ml. 3. Serum thyrotrophin (TSH) concentration was raised in cord serum compared with maternal serum.

Technological developments have brought increasing needs for convenient, portable instruments for measuring current and voltage with high accuracy over a wide range of frequencies. A ?universal? volt-ampere (VA) converter has been developed for making such measurements to 0.05% with alternating current at frequencies from 5 cps (cycles per second) to 50 kc and with direct current. The new model is based on an earlier, much more limited prototype converter,1 and, like it, is used with a null-type d-c potentiometer. With this single, self-contained, portable, 44-range instrument, the 1.5-volt range of a suitable potentiometer can be used to make a-c (rms) and d-c measurements from 7.5 milliamperes (ma) to 20 amperes and from 0.5 volt to 600 volts. With a more sensitive external galvanometer, the instrument can also be used as an a-c-d-c transfer standard for a-c-d-c difference measurements to 0.02% over the same frequency range.

Poisoning with aflatoxin derived from mouldy bread was confirmed as the cause of death of one dog and was suspected as the cause of death of two other dogs on the same ration. A jaundiced carcass, firm bile-stained liver and haemorrhage into the gastro-intestinal tract were seen at autopsy. Swelling and foamy vacuolation of hepatocytes due to fatty infiltration, marked perioportal proliferation of bile ductules and some periacinar necrosis were the microscopic changes seen in the liver. Aspergillus flavus was isolated from the mouldy bread and also from a sample of vomitus. Aflatoxin B1, 6.7 ppm, was detected in the mouldy bread and extremely high levels of 100 ppm of aflatoxin B1 and 40 ppm of aflatoxin G1 were present in a sample of vomitus.

A thyrotropin (T.S.H.) test is suggested which relies on the change in the concentration of serum thyroxine as the index of thyroid response to T.S.H. stimulation. Ten such tests have been carried out in healthy volunteers and 39 in patients referred for routine thyroid stimulation tests. Among the advantages of such a test are that the patient does not receive ionizing radiation; it is independent of the presence of iodide-or mercury-containing compounds; and it minimizes the number of patient visits. In remote areas the patient need not attend the specialist centre, because the T.S.H. injection can be given and the serum samples taken locally, the samples then being sent to the appropriate laboratory for assay.

IT has been shown1 that during a prolonged stay at altitudes above 15,000 ft. there is an increase in the salivary excretion of sodium and a decrease in that of potassium. In one subject this change in salivary electrolyte composition showed a marked acclimatization effect (Fig. 1). These findings suggested that, on arrival at a high altitude, the level of circulating aldosterone was likely to be greatly reduced, but that there would probably be a tendency for it to return slowly towards normal values with passage of time.

A thyroid suppression test is suggested which relies on the change in concentration of serum thyroxine as the index of thyroid response to the administration of triiodothyronine. The test has been carried out in 16 healthy volunteers and in 27 patients referred for routine suppression tests. This index appears to be sensitive and safe and results in a reduction in the required dosage of triiodothyronine. The test can be carried out in fewer patient-visits than the commonly used suppression test; moreover, in remote areas the patient need not attend the specialist centre because the course of triiodothyronine can be given (and the serum samples obtained) locally, the samples then being sent to the appropriate laboratory for assay.

It may be of interest to compare the changes in the normal range of thyroidal radioiodine uptake as reported by Kirkman (1974) with those we have reported (Keeling and Williams, 1972). The main feature is the similarity of the findings: a “drift” of the average uptake in a group of euthyroid subjects to lower values over the last (approximately) decade and a half, with latterly a reduction in the magnitude of the change. In both Kirkman's and our studies the results suggested that a small reduction was continuing but in neither series were the recent results significantly different from those obtained in the middle to later 1960s.

1. Four men, of ages varying from 23 to 28 years, living at Halley Bay, Antarctica (75 degrees 31' S, 26 degrees 39' W), were exposed to a mean air temperature of 6.6 degrees C.2. The concentration of serum triiodothyronine (T(3)) rose significantly by the second day, remained raised, and returned to pre-exposure levels within 2 days of return to a normal environment.3. The concentration of serum thyroxine (T(4)) rose more slowly than did the T(3), reaching a maximum in 3-4 days and also returning to normal within 2 days of return to a normal environment.4. There was a wide individual variation in the change of concentration of serum cortisol.

Three series of patients shown to be euthyroid but originally referred for thyroid uptake tests in vivo have been compared. In 1958-59, the `normal9 mean thyroid uptake was 23·5% and 38·2% respectively at four and 24 hours. By 1967, the mean uptakes had dropped to 20·4% and 31·6%—a significant change at both times. By 1972 there was, however, no sign of a further reduction of the mean normal values for thyroid uptake. These results are compared with changes observed in other series in the USA and elsewhere.

Until the middle 1960s, almost all reports in the literature relating to the safety of radio-pharmaceuticals referred only to radiation hazards. Accounts of specific adverse effects were also of this nature, usually an accidental over-exposure to radiation. A scattered literature later began to appear recording adverse reactions to the vehicle carrying the source of radiation and similar reports were from time to time mentioned among colleagues. During approximately the last decade there has been an explosive increase in the clinical usefulness of imaging using radioactive tracers. In part, this has been a result of improved instrumentation but a significant factor has been the introduction of a variety of vehicles for the radioactive tracer chosen. During roughly the same period, methods have been developed to make short-lived nuclides available at the site of use by elution from a column containing the longer-lived parent. This gave new impetus to the search for chemicals having desirable organspecific ...