Insulin-like growth factor I receptor primary structure: comparison with insulin receptor suggests structural determinants that define functional specificity.

To identify structural characteristics of the closely related cell surface receptors for insulin and IGF-I that define their distinct physiological roles, we determined the complete primary structure of the human IGF-I receptor from cloned cDNA. The deduced sequence predicts a 1367 amino acid receptor precursor, including a 30-residue signal peptide, which is removed during translocation of the nascent polypeptide chain. The 1337 residue, unmodified proreceptor polypeptide has a predicted Mr of 151,869, which compares with the 180,000 Mr IGF-I receptor precursor. In analogy with the 152,784 Mr insulin receptor precursor, cleavage of the Arg-Lys-Arg-Arg sequence at position 707 of the IGF-I receptor precursor will generate alpha (80,423 Mr) and beta (70,866 Mr) subunits, which compare with approximately 135,000 Mr (alpha) and 90,000 Mr (beta) fully glycosylated subunits.     

The effect of oxygen on nitrate and nitrite assimilation in leaves of Zea mays L. under dark conditions

The assimilation of nitrate under dark-N₂ and dark-O₂ conditions in Zea mays leaf tissue was investigated using colourimetric and ¹⁵N techniques for the determination of organic and inorganic nitrogen. Studies using ¹⁵N indicated that nitrate was assimilated under dark conditions. However, the rate of nitrate assimilation in the dark was only 28% of the rate under non-saturating light conditions. No nitrite accumulated under dark aerobiosis, even though nitrate reduction occurred under these conditions. The pattern of nitrite accumulation in leaf tissue in response to dark-N₂ conditions consisted of three phases: an initial lag phase, followed by a period of rapid nitrite accumulation and finally a phase during which the rate of nitrite accumulation declined. After a 1-h period of dark-anaerobiosis, both nitrate reduction and nitrite accumulation declined considerably. However, when O₂ was supplied, nitrate reduction was stimulated and the accumulated nitrite was rapidly reduced. Anaerobic conditions stimulated nitrate reduction in leaf tissue after a period of dark-aerobic pretreatment.     

Generation of natural killer-like cytotoxicity from human thymocytes with interleukin-2

Human thymocytes cultured in the presence of an interleukin-2 (IL-2) source (the supernatant of the MLA 144 cell line) that contains no lectin or interferon (IFN) activity become cytotoxic to K562 target cells. Inclusion of allogeneic lymphoblastoid cells in these cultures results in the earlier detection of cytotoxic activity. Addition of IFN to the thymocyte cultures has no effect on the development of cytotoxic activity. In contrast, the cytotoxic activity of IL-2 activated thymocytes can be augmented by subsequent exposure to IFN. The specificity and cell surface phenotype of the cytotoxic thymocytes are similar to that of peripheral blood natural killer cells.     

Effect of solubilization on adenosine 5'-triphosphate induced calcium release from purified sarcoplasmic reticulum calcium adenosinetriphosphatase

ATP-induced Ca2+ release from the purified sarcoplasmic reticulum Ca2+-ATPase has been monitored in several different ATPase environments. Arsenazo III was used as a Ca2+ indicator in stopped-flow experiments and was shown to detect the early burst in Ca2+ transport, slower steady-state transport, and release of Ca2+ from fragmented sarcoplasmic reticulum. ATP-induced rapid release of Ca2+ followed by a slower rebinding step could be demonstrated for purified Ca2+-ATPase in leaky vesicles if the reaction was slowed by lowering the pH to 6.1 and by including dimethyl sulfoxide in the reaction medium. At a dodecyl octaoxyethylene glycol monoether (C12E8) to protein weight ratio of 0.2, a detergent concentration too low for solubilization to occur, ATP-induced Ca2+ release occurred more rapidly than for native leaky membranes, whereas the rebinding step was slower. In contrast, no Ca2+ release was observed for any soluble preparation. The kinetics of Ca2+ release was studied under conditions where the ATPase was monomeric or aggregated, and also in the presence of added phospholipid. The ATPase was shown to be monomeric by sedimentation equilibrium measurements in the presence of Ca2+, ADP, and beta, gamma-methylene-ATP at a C12E8 to protein weight ratio of 2.0. It is concluded that solubilization of the Ca2+-ATPase may result in uncoupling of ATP hydrolysis from ATP-induced Ca2+ release.     

High Dosage Metolazone in Chronic Renal Failure

Metolazone is a modified quinazolinesulphonamide and in a dose of between 4 and 7·5 mg is an effective diuretic in man with normal renal function. Fourteen patients with non-oedematous stable chronic renal failure (creatinine clearance ranging from 1·2 to 12 ml/min) were given metolazone in doses ranging from 20-150 mg. A noticeable increase in urine flow and sodium excretion occurred, free water clearance increased, and there was a small but significant increase in potassium excretion. No side effects were noted.     

The circular dichroism of poly d(AAT): d(ATT) and poly r(AAU):r(AUU). A test of the first-neighbor hypothesis

We present absorption and circular dichroism (CD) spectra for the synthetic polymers poly d(AAT):d(AAT) and poly r(AAU):r(AAU), in both native and heat-denatured forms. As a means of evaluating the first-neighbor hypothesis, the CD spectra are compared with approximations derived from spectra of other synthetic polymers containing the same first-neighbor sequences. This is the first instance where such a comparison has been possible using spectra of double-stranded RNA sequences, and the agreement between the measured and approximated spectra for poly r(AAU):r(AUU) is surprisingly good. We have also subjected the CD spectrum of poly d(AAT):d(AAT) to a previously published analytical procedure for obtaining estimates of first-neighbor frequencies. In this first independent test of the procedure, we find that the analysis does infer the existence of a majority (86%) of AA, TT, AT, and TA first neighbors but does not precisely indicate their relative proportions.     

Application of Urine Analysis to Diagnosis and Treatment of Heroin Addiction

Experience with urine analysis for morphine using thin-layer chromatography in 310 cases of real or possible heroin abuse showed that it was valuable not only in detecting improper drug use but also in monitoring treatment. The results of this test can be available routinely in 24, and exceptionally in five hours. A negative result implies that the subject has taken less than 10 mg. of heroin in the past 24 hours.     

Saccharomyces capensis - an inositolless yeast

Saccharomyces capensis (N.I.U. No. 309) has been shown to have an absolute requirement for inositol and a partial requirement for biotin and pantothenate. Since the relation between growth of this yeast and concentration of inositol is nearly linear in the range of 0.18 to 1.0µg/ml of medium,S. capensis is an excellent organism to use for the bioassay of inositol.

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Zusammenfassung Saccharomyces capensis (N.I.U, no. 309) zeigte ein absolutes Erfordernis für Inositol und ein Teilerfordernis für Biotin und Pantothenate. Da die Beziehung zwischen dem Wachstum dieser Hefe und der Konzentration von Inositol beinahe linear im Bereich von 0.18 bis 1.0µg/ml des Nährbodens ist, istS. capensis ein vorzügliches Objekt für Bioassay von Inositol.

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The writers are indebted to Dr. L. R. deMiranda, Centraalbureau voor Schimmelcultures Baarn, the Netherlands for the identification of this yeast.