HPLC shadowing: Artifacts in peptide characterization monitored by RIA

High performance liquid chromatography (HPLC), a valuable tool for characterization of peptides, is frequently used in combination with sensitive radioimmunoassays (RIA). The shadow phenomenon, representing carry-over of the peptide from previous application of the standard, can appear to result in the presence of endogenous peptide in the test sample when none is actually there. With delta sleep-inducing peptide (DSIP), we found the shadowing to be as high as 10%, although it was only 1% with ¹²⁵I-Tyr-DSIP. Thus, when HPLC-RIA systems are used for identification of peptides, caution must be used to avoid false positive results.     

Hematochemical parameters in sheep and goats of Sardinian breeds. II) Total blood cholesterol

It has been studied the total plasma cholesterol rate in lactating or dry sheep and goats of Sardinian breed. The values obtained for the four different groups of subjects have been compared with the "t of Student". While the difference between the sheep groups has seemed very accentuated, it has appeared hardly significant between the goat groups. Highly significant difference has also been found between lactating sheep and goats whereas there was no significant difference among the groups of dry subjects.     

Changes in intracellular proteolysis in Escherichia coli during prolonged growth with a low concentration of dihydrostreptomycin

Abstract Escherichia coli was cultured with a low concentration of dihydrostreptomycin (2.5 μg/ml.). Growth was similar to untreated controls for 10 h after which a slow decline in growth rate occurred; growth ceased after 20 h. Intracellular catabolism of pulse-labelled protein synthesised at various points during the antibiotic treatment increased during the first 10 h, but during the second 10 h proteolysis progressively declined to almost control values. The production of an aberrant proteolytic system is one possible explanation.     

Synchronization of drosophila cells in culture

Summary We synchronized Drosophila cell lines (Schneider's line 2 and K_c) by allowing the cells to enter the stationary phase of growth and then diluting them into fresh culture medium. The cells of both cell lines entered S phase, after an 8- to 14-hr delay, in a state of partial synchrony; 60 to 80% of the cell population accumulated in S phase. Measurements of the cell cycle phases of Schneider's line 2 cells (S=14 to 16 hr; G₂=6 to 8 hr; M=0.4 hr) were similar to those of K_c cells. This work was performed under the auspices of the U.S. Energy Research and Development Administration. A.R. was supported by an NIH post-doctoral fellowship, No. CA01060.     

The importance of birds in the dispersal of nuclear polyhedrosis virus of European spruce sawfly, Gilpinia hercyniae (Hymenoptera: Diprionidae) in Mid-Wales

The discovery of nuclear polyhedrosis virus disease (NPV) of Gilpinia hercyniae (Hartig) in bird droppings had given rise to the suggestion that birds might be important in virus dispersal. Advantage was taken of the continuing spread of sawfly and virus to sample larvae in an area with sawfly and virus, and in adjacent areas with sawfly only: bird dropping were also collected in the latter. In the previously virus-free areas, NPV was identified in some larvae but not in bird droppings. It is therefore suggested that sawfly adults might be major agents of dispersal.

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Résumé La découverte du virus de la polyédrose nucléaire (NPV) dans les excréments d'oiseaux a conduit à penser que ces derniers pourraient jouer un rôle important dans la dispersion de ce virus. On a profité du fait de l'extension continue de la tenthrède et de son virus, pour sélectionner et échantillonner d'une part des larves de tenthrèdes, d'autre part des excréments d'oiseaux, dans des zones contaminées ou non par le virus. Dans les zones non encore atteintes par l'épidémie de la virose, le virus NPV fut cependant identifié dans quelques larves mais non dans les excréments d'oiseaux. Il est donc suggéré que les tenthrèdes adultes pourraient être les agents principaux de la dispersion du virus.

     

Secretion of lysosomal enzymes by human placental villi in vitro

Summary Chorionic villi from first trimester and term human placentas have been incubated in vitro and shown to release the lysosomal enzymes, -hexosaminidase, -glucosidase and -gluctlronidase. There was negligible release of the cytoplasmic enzyme, lactate dehydrogenase, under the same conditions. The first trimester villi released proportionally more of their lysosomal enzyme content than did the term villi. Extracellular levels of -hexosaminidase were raised and those of -glucosidase and, -glucuronidase were lowered when tissue was incubated with 1 M colchicine, suggesting that microtubules are involved in the control of lysosomal enzyme release from placental villi.     

The influence of zooplankton food resources on the morphology of the estuarine clupeid Gilchristella aestuarius (Gilchrist, 1914)

Synopsis The body shape of the estuarine clupeidGilchristella aestuarius from the St. Lucia system is different from that of the same species in other estuaries. The morphology ofG. aestuarius is discussed in relation to long term food availability in the St. Lucia system.     

Temperature response of the cell cycle of Haplopappus gracilis in suspension culture and its significance to the G1 transition probability model

The effects of temperature on the cell cycle of Haplopappus gracilis suspension cultures were analysed by the fraction of labelled mitoses method. Sphase in these cultures shows a different temperature optimum as compared to optima derived for G₂ and mitosis. G₁ phase has a much lower Q₁₀ than the other cell cycle phases and shows no temperature optimum between 22 and 34° C. These results are discussed in relation to a transition probability model of the cell cycle proposed by Smith and Martin (Proc. Natl. Acad. Sci. USA 70, 1263–1267, 1973), in which each cell has a time independent probability of initiating the transition into another round of DNA replication and division. The implications of such a model for cell cycle analysis are discussed and a tentative model for a probabilistic transition trigger is advanced.Abbreviations FLM Fraction of labelled mitoses - T_B Total B-phase