The synthesis of 15N- and deuterium-substituted, spin-labeled analogues of NAD+ and their use in EPR studies of dehydrogenases

Calcium efflux and EGTA-induced calcium release from an internal platelet membrane fraction have been studied after the oxalate-supported calcium uptake had reached steady state. Increasing external calcium concentrations stimulate the calcium efflux velocity, with an apparent half-maximal stimulation at about 5 microM outside calcium concentration and a maximal velocity of calcium efflux of 4.66 +/- 2.32 nmol X min-1 X mg-1. Moreover, the ratio of the liberated calcium on the loaded calcium seems to be independent of the increasing external calcium concentration. Increasing the calculated internal calcium concentration by varying the oxalate potassium concentration from 10 mM to 1 mM results in an increase of the liberated calcium from the membrane vesicles from 7.4% to 63%, respectively, without changing the calcium efflux velocity. Similar conclusions can be drawn from the observation of results from the calcium efflux and EGTA-induced calcium release methods. Moreover, calcium pump reversal does not seem to be responsible for the calcium efflux or calcium release. All these different points added to the previously described regulation of calcium efflux by the catalytic subunit of cAMP protein kinase suggest us that the mechanism of calcium liberation by the platelet membranes is different from the calcium uptake.     

Monitoring the integrity of self: biology of MHC-restriction of virus-immune T cells

All available evidence indicates that the cytotoxic thymus-derived lymphocyte (T cell), which is lytic for virus-infected target cells in vitro, is also the effector in cell-mediated immunity in vivo. Such T cell show two orders of specificity: for the virus in question, and for a particular self major histocompatibility complex (MHC) glycoprotein. Recirculating T cells amy thus be considered to survey the integrity of self, the self components involved being the cell-surface structures that are recognized as foreign during graft rejection. Virus-infected liver cells are apparently eliminated in much the same way as a transplanted organ. The necessary balance between self-tolerance (absence of autoreactivity) and self-monitoring effector T cell function seems to be established during the process of differentiation in thymus. The molecular nature of the underlying recognition events is, as yet, obscure.     

Early growth and final yield of autumn sownVicia faba L cultivars given different forms of fertiliser N over winter

Summary Between 3 Nov. 1983 and 9 Apr. 1984, six applications of fertiliser N (ammonium, nitrate or urea) were given to four autumn sown (26 Oct. 1983)Vicia faba L cultivars, Banner Winter (BW) and Maris Beagle (MBg), cold tolerant cultivars normally sown in the autumn, and Herz Freya (HF) and Maris Bead (MBd), cold sensitive cultivars more commonly sown in the spring. The effects of additional N were determined by comparison with plants given zero-N (controls). Application of N, regardless of form, had no effect on % emergence at the first sampling (15 Dec. 1983); >90% for BW, MBg and HF, but only 40–60% for MBd. At this time the dry weight, carbon content and nitrogen content of all cultivars was approximately 20% less than that of the seed on planting. No more plants emerged after 15 Dec. 1983. Between 15 Dec. 1983 and 20 Feb. 1984, all cultivars, regardless of N treatment, showed little change in dry weight, carbon content and nitrogen content but the proportion of total plant dry weight, carbon content and nitrogen content in the cotyledons decreased while the proportions in root, stem and leaf tissue increased. On 20 Feb. 1984 there were no N effects. All cultivars but especially BW and MBg, showed progressive increases in dry weight, carbon content and nitrogen content during the period 20 Feb. 1984 to 8 May 1984. Pooled results for all four cultivars indicated that on 8 May 1984, plants given ammonium and urea had a greater dry weight, carbon content and nitrogen content than controls. At harvest (1–3 Sep. 1984), BW and MBg outyielded (g dw seed m⁻²) HF and MBd. Pooled results for all cultivars indicated that application of N regardless of form gave increased yield and an increased N concentration (mg N g⁻¹ dw) in the seed.     

Quantitative histology of the hypertrophied human heart

Myocardial hypertrophy accompanies systemic hypertension and aortic stenosis, i.e., pressure overload. In man cardiac failure only appears after years of pressure overload, during which time cardiac function had been maintained. The structural correlates of cardiac failure have been a subject of much interest for many years. Several hypotheses relating alterations in muscle fiber alignment, capillary density, or collagen content have been offered. The application of morphometric techniques has provided essential quantitative information on the structural components of the normal and diseased heart. These data indicate that muscle fiber alignment remains normal in the pressure overloaded heart despite the presence of hypertrophy or the appearance of clinical failure. On the other hand, capillary density is decreased and collagen content is increased in hypertrophied hearts. Chemical studies on collagen concentration however have yielded inconsistent results. The relative contribution of the microcirculation and collagenous structure of the myocardium on its respective O2 availability, mechanical behavior, and deterioration in pump function will require further investigation.     

Methods for study of mutations and mutagenesis in human lymphocytes

Detailed methods are presented for measurement and study of in vivo mutations and in vitro mutagenesis in human lymphocytes. The methods described include preparation of conditioned medium containing interleukin-2, enumeration of mutant clones, in vitro mutagenesis, and expansion of mutant clones for further study.     

Studies on functional domains of the regulatory subunit of bovine heart adenosine 3':5'-monophosphate-dependent protein kinase

The functional domains of the regulatory subunit of isozyme II of cAMP-dependent protein kinase were studied. It was shown using Edman degradation that the regulatory subunit contained a phosphorylated residue which was very close in primary sequence to the site most sensitive to hydrolysis by low trypsin concentrations as postulated previously (Corbin, J.D., Sugden, P.H., West, L., Flockhart, D.A., Lincoln, T.M., and McCarthy, D. (1978) J. Biol. Chem. 253, 3997-4003). Catalytic subunit incorporated 0.9 mol of 32P from [gamma-32P]ATP into a preparation of regulatory subunit that contained 1.1 mol of endogenous phosphate. After phosphorylation by the catalytic subunit, the regulatory subunit contained 2.2 mol of chemical phosphate. The effects of heat denaturation upon the rate and extent of phosphorylation of the regulatory subunit were compared with the effects of these treatments upon the cAMP binding and inhibitory domains. These data suggested that the regulatory subunit required factors in addition to an intact phosphorylatable primary sequence in order for inhibitory activity to be expressed. Such factors might be part of the secondary or tertiary structure of the protein. These studies are discussed with respect to the mechanism of inhibition of catalytic activity, and a model of the regulatory subunit structure is proposed.