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1. Evidence for the occurrence of a rapidly polymerizing equilibrium system in freshly prepared aqueous solutions of porcine neurophysin has been obtained by frontal and zonal analysis of gel-filtration elution patterns. 2. Elution volumes increased with decreasing protein concentration and derivative analysis of fronts suggested the existence of different polymerizing forms varying in relative proportion with protein concentration. 3. In the presence of lysine vasopressin, the results suggested a shift of the equilibrium in favour of higher polymerizing forms. 4. In the presence of Ca2+ elution patterns became characteristic of a monodisperse system of relatively high molecular weight. The effect of Ca2+ did not survive removal of the ion and was not reproduced by Mg2+. 5. Evidence for a slowly developing polymerization of neurophysin in aqueous solution has been obtained in experiments with solution prepared 24 hr before subjection to gel-filtration. 6. A model is proposed for the description of the binding of lysine vasopressin to porcine neurophysin.

A method is described for the rapid separation of cells from their suspending medium with only 1 5 th to 1 30 th the amount of contamination from the medium as with conventional centrifuging. The principle is to interlayer between the cells and the medium upon centrifuging an immiscible liquid whose density lies between that of the cells and medium. Quantitative measurement of the amount of contamination of the cells by the medium which does occur is achieved by adding a nonpermeable radioactively labeled substance to the suspension prior to centrifugation.

1. The concentration of Bromophenol Blue used as tracking dye in polyacrylamide-gel electrophoresis affected the resolution of rat neurophysins. 2. A final dye concentration of 1μg/ml in the tris–glycine running buffer was found to give the best results. 3. The presence of two major and one minor neurophysin(s) in the rat was confirmed. 4. The two major proteins were found to re-run as single discrete bands, which had the same mobilities in the absence of dye and different mobilities in its presence.

Publisher Summary This chapter presents three basic methods for the analysis of (Na, K, Mg, Ca, Mn, Fe, Co, Cu, Zn) elements. First, a rapid, sensitive colorimetric procedure is given that can be readily utilized for routine analyses of medium precision. A volumetric method is included for requirements of precision of an order of magnitude greater than that available by colorimetry, and gravimetric methods are presented because they are applicable to radioactive tracers. In a number of cases the selection of three such methods is not necessary, because one may have little advantage over another. One special instrumental method of analysis has been included as a separate section in view of its wide usage and applicability to elements that are otherwise difficult to determine— namely, the flame photometry of the alkali metals and alkaline earths. Flame attachments for spectrophotometers have become so widespread that it is rare to find a laboratory which does not somewhere have a flame attachment available. Certainly, when the equipment is available, this becomes the method of choice for the alkali metals and alkaline earths.

Substances that have not exhibited properties as excitants of ectopic activity by intracoronary injection into normal hearts often produce rapid ectopic activity and sometimes ventricular fibrillation upon slow injection through the vascular bed of an infarcted area, particularly upon the first one or two injections. Sodium lactate has reduced and stopped ectopic activity for brief periods. Excesses of both potassium and calcium have increased ectopic activity in infarction and produced it in normal hearts. No antagonism between these two ions, with respect to ectopic activity, has been demonstrated.

Many of our current ideas of the dynamics of neurosecretory neurones come from contributions by microscopists who have studied their structure in animals in different physiological conditions. These findings have provided the basis for discussion at each of the previous Symposia on Neurosecretion and the purpose of this paper is to review the extent of biochemical support that exists for these current concepts, although rather more examples will be drawn from the work of our own laboratory than its importance might warrant.

The change in the radioactivity of vasopressin–neurophysin in the rat neurohypophysis after an intracisternal injection of [35S]cysteine was fitted to several mathematical models. The data fitted best a model in which there is a linear input of radioactive protein into one pool of the neurohypophysis, from which it is either released by an exponential process or transferred to a second pool from which it is released by a second exponential process with a rate constant much lower than the first. This model is compatible with the existence of a ‘readily releasable’ pool first postulated by Sachs et al. (1967). Data for the change in radioactivity of vasopressin also gave a good fit in this model. Calculation of the rate constants suggested that the first pool represented about 2% of the total hormone.

1. Rat neurohypophysial extracts have been examined by polyacrylamide-gel electrophoresis. 2. Three of the proteins were tentatively identified as neurophysins by their acidic nature and their disappearance after dehydration of the animals. 3. These proteins were radioactive 24h after intracisternal injection of [35S]cysteine. 4. Two of the proteins were present in much greater quantities than the third, and these two were present in the gland in the same ratio as the hormones vasopressin and oxytocin. 5. One of these proteins was absent from glands of rats homozygous for diabetes insipidus but present in heterozygous animals. 6. It is suggested that these two proteins are the vasopressin–neurophysin and oxytocin–neurophysin of the rat.

1. 1.|The object of the investigation was to determine the molecular weight of neurophysin polypeptide chains and to test the hypothesis that these exist in polymerising equilibrium. 2. 2.|Polyacrylamide gel electrophoresis of a denatured porcine neurophysin preparation in the presence of detergent revealed three components, two major and one minor, of molecular weights ⩽ 10 000, ⩽ 12 000 and ≈ 14 000, respectively. 3. 3.|The weight-average molecular weight of the porcine neurophysin preparation was estimated by analytical ultracentrifugation and with the denatured protein was 11 000, and independent of protein concentration. With undenatured protein the weight-average molecular weight increased (at pH 5.8) with concentration from approx. 10 000 to approx. 35 000 and the influence of protein concentration was pH dependent. 4. 4.|In the presence of Ca 2+ (1 · 10 −5 M at pH 5.8) the weight-average molecular weight of porcine neurophysin was 21 000 and was independent of protein concentration. 5. 5.|It is concluded that neurophysin monomers consist of single polypeptide chains, which in aqueous solution, exist in polymerising equilibrium and that equilibrium is perturbed by Ca 2+ .