PREVIOUS papers from this laboratory have dealt with the application of the titration method with 2: 6-dichlorophenolindophenol to the estimation of vitamin C in various animal materials [Harris and Ray, 1933, 1, 2; Birch et al., 1933; Birch and Dann, 1933; Harris, 1933]. Results on human urines are discussed in the present communication. A principal purpose we had in mind in undertaking this enquiry was to discover whether any relation could be found between urinary loss and the state of nutrition of the individual in respect to vitamin C sufficiency or subnormality. Any such index would obviously be of great value for practical human dietetics.Previous biological work has failed to demonstrate the presence of vitamin C in urine [van der Walle, 1922], but a note just published by Eekelen et al. [1933] mentions, without giving actual data, that the reducing substance in urine is higher in persons using much fruit. METHOD.The micro-method of Birch et al. [1933] was used throughout. The urine to be examined was made acid with trichloroacetic acid (final concentration of latter, 5 %) and titrated from a micro-burette reading to 0 01 cc. against 005 cc. of the indicator, which had been previously standardised against ascorbic acid. Titrations were carried out immediately after, or within a few minutes of, urination, as we found that the titre tended to fall in urine which had been allowed to stand for long. It is essential to carry out the titration rapidly and reach the end-point within about 1 min., otherwise erroneously high values will be caused by phenolic or similar substances in the urine reducing. the indicator slowly. Urines are sometimes encountered which are too dilute to give a satisfactory end-point. If a reading is required for such an individual it is necessary to restrict his fluid intake. The results to be described make it clear that the titration figure bears a genuine relation to vitamin C metabolism, but in expressing our results for convenience in terms of so many mg. of ascorbic acid we wish to. make it clear that it is without prejudice to the question of the invariable specificity or otherwise of the reaction. EXPERIMENTAL.Excretion after large dose. Our most detailed observations were undertaken with the object of obtaining a quantitative picture of the course of excretion of the vitamin after the administration of a single large dose. These results will be

Transient changes in the concentration of intracellular free calcium are associated with the transduction of primary signals and the subsequent employment of Ca2+ as a second messenger in a multitude of cell types. These transients, typically monitored with the calcium-sensitive fluorescent dye Fura-2, are known to occur with a time course in the order of seconds. In order to accurately monitor such rapid changes in intracellular free calcium concentration in both single cells and simultaneously in several cells in a single field, we have developed a digital fluorescence imaging system based on a charge-coupled device (CCD) camera. We report here on the detailed kinetics of calcium increases in cultured arterial swine smooth muscle cells in response to the agonist ATP.

Until abouit 8 years ago the only method for determining vitamin C was by means of biological tests on guinea-pigs. In consequence, knowledge about the distribution and behaviour of the vitamin accumulated slowly and with difficulty, and it was not until a chemical method had been introduced that progress became more rapid.

In this investigation we tested the hypothesis that static body condition (BC) of the ewe affects oestradiol and FSH with implications for subsequent follicular growth and turn-over. Sixteen Polwarth ewes were selected from a flock according to their BC score (scale: 1 emaciated; 5 obese). High BC (HBC) ewes (no. = 8) had a BC score of 4·1 (s.e. 0·1) and low BC (LBC) ewes (no. = 8) had a BC score of 1·9 (s.e. 0·1). Daily ultrasound examinations were performed and blood samples for progesterone, oestradiol and follicle-stimulating hormone (FSH) determination were collected. All HBC ewes (8/8) exhibited three waves of follicular development, while four LBC ewes (4/8) had two waves and the other four (4/8) had three waves of follicular development (P ≤ 0·05) during the interovulatory period. Overall, the emergences of 33 out of 44 follicular waves were preceded by significant increases in FSH concentrations. Maximum FSH concentrations were detected 0·9 ± 0·2 days before wave emergence. Oestradiol concentrations increased significantly during the growing phase in 38 out of 44 large follicles. A negative correlation between oestradiol and FSH was observed in HBC ewes. A similar inhibitory effect of oestradiol on FSH was observed in LBC ewes, irrespective of whether they developed two or three follicular waves. However, a longer period with high FSH was needed to promote the emergence of the second follicular wave in two-wave LBC ewes. Four HBC ewes had twin ovulations but no LBC ewes did (P ≤ 0·05). In HBC ewes, the follicular phase was characterized by lower oestradiol (6·5 (s.e. 1·0) pmol/l) but higher mean FSH concentrations (2·4 (s.e.0·4) μg/l) than in LBC ewes (8·9 (s.e. 1·2) pmol/l and 2·0 (s.e. 0·3) μg/l, respectively; P ≤ 0·05). The present results suggest that BC influences the pattern of follicular dynamics through changes in the endocrine milieu. Higher FSH concentrations during the follicular phase in HBC ewes, which allowed an extended period of follicular recruitment from a significantly larger pool of small antral follicles could explain the higher ovulation rate observed in this group.

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IN earlier work [Harris & Leong, 1936; Harris et al. 1938] it was shown that the extent of the body's "reserves" of vitamin B1 might be measured by means of a test on the urine, similar in principle to that previously introduced for vitamin C [Harris et al. 1933; Harris & Ray, 1935]. The urinary output was found to depend on the past intake, being negligible in beri-beri or in "conditioned" deficiencies of vitamin B1 and being lowered in certain other abnormal states.To simplify the procedure, several investigators [e.g.

It has often been assumed that animals given a suitable free choice of diets are able to select satisfactorily according to their individual nutritional needs. However, no systematic work has hitherto been undertaken to ascertain how far this is true, nor have we any knowledge of the mechanism involved in the choice. Lusk (1928), in his well-known text book on nutrition, refers to the observation of a German worker (Tscherkes, 1923) that fowls suffering from polyneuritis will search out green food and refuse to accept grain. This be describes as due to the "triumph of instinct." The similar eagerness of vitamin B deficient rats to consume diets containing the vitamin must, we imagine, have been noticed by observant workers. It is, however, unsatisfactory to allow the matter to be ascribed vaguely to some unexplained—it nor inexplicable—" instinct." It animals are in tact able to distinguish between foods containing and deficient in the vitamin, what is the nature of the process involved? Has the animal some means, as by taste or smell, of recognizing the vitamin per se ? It so, it would imply an ability to detect a constituent amounting to no more than perhaps 1 part in a million of the food. It nor, by what means is the rat able to recognize the vitamin-containing food ? And what are the limitations to such powers of recognition ? These are some of the questions which one sought to answer, An effort to analyse these phenomena was begun in this laboratory in 1928, and in the present paper are summarized the principal results reached during the period 1928-1931.* To anticipate a main conclusion it max be said at once that we have obtained good evidence that the behaviour of the animal is due not so much to instinct as to experience, i. e ., of the beneficial effect produced by a particular foodstuff. We believe that This factor of experience plays an important part in determining dietary preferences in general, and it will certainly have to be taken into account in future work on that hitherto neglected subject, the psychology of appetite. Apart from the reference quoted above we know of no previous literature relating to the original point of departure of our enquiries. Recorded work on the whole question of the free choice of diet is almost equally scanty. Osborne and Mendel (1918), working on the comparative food values of different proteins, thought that rats " as a rule ate more of the adequate than of the inferior food " ; but Beadles, Braman and Mitchell (1930), on the contrary, could find " no support for the assumption that the more complete of the two rations is consumed in greater amount." Nevens (1928) noted that cattle given a free choice of limestone, bone meal and salt, offered as supplements to an inadequate diet, took only insignificant amounts of the first two ; while kon (1931) found that rats might fail to take enough protein even to keep them alive, when allowed to choose their own allowance of carbohydrate, protein and salt mixture.

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