Restriction endonuclease and nucleotide sequence analyses of molecularly cloned unintegrated avian tumor virus DNA: structure of large terminal repeats in circle junctions

Avian tumor virus supercoiled DNA was isolated from infected quail tumor cells and molecularly cloned in pBR322. Four different recombinant clones denoted pATV-6, pATV-7, pATV-8, and pATV-9 were characterized in detail by restriction endonuclease mapping and by DNA sequencing. The results of these studies indicate that (i) the two large terminal repeats (LTRs) present in PATV-6, are different sizes, (ii) pATV-8 and pATV-9 contain only one LTR, (iii) pATV-7 contains an inversion of 0.6 kilobase in the env gene and a deletion of the U3 region and the src gene, and (iv) the src gene is deleted in pATV-6 and pATV-9. Circle formation from linear molecules was also examined in several of the clones by DNA sequencing through the circle joint. pATV-6 is an example of one class of circular molecules and contains a partially repeated LTR similar to that reported by Ju and Skalka (Cell 22:379-386, 1980). A second class of circles was exemplified by pATV-8 and pATV-9, which contain a single copy of the LTR with no base changes or deletions. This is in contrast to a class of circles containing a complete double LTR structure described by Swanstrom et al. (Proc. Natl. Acad. Sci. U.S.A. 78:124-128, 1981) and suggests that circles containing a single intact LTR may be formed by a homologous recombinational event in which an entire LTR or complementary regions from both LTRs are removed from the linear DNA molecule during circularization.     

Time-dependent changes of calcium influx and efflux rates in rabbit skeletal muscle sarcoplasmic reticulum

Unfractionated and low buoyant density sarcoplasmic reticulum vesicles released calcium spontaneously after ATP- or acetyl phosphate-supported calcium uptake when internal Ca²⁺ was stabilized by the use of 50 mM phosphate as calcium-precipitating anion. This spontaneous calcium release could not be attributed to falling Ca²⁺ concentration outside the vesicles (Ca₀²⁺), substrate depletion, ADP accumulation, nonspecific membrane deterioration or the attainment of a high vesicular calcium content. Instead, spontaneous calcium release was directly proportional to Ca₀²⁺ at the time that calcium content was maximal. A causal relationship between high Ca₀²⁺ and spontaneous calcium release was suggested by the finding that elevation of Ca₀²⁺ from less than 1 μM to 3–5 μM increased the rate and extent of calcium release.The spontaneous calcium release was due both to acceleration of calcium efflux and slowing of calcium influx that was not accompanied by a significant change in the rate of ATP hydrolysis. Neither reversal of the transmembrane KCl gradient nor incubation with cation and proton ionophores abolished the spontaneous calcium release. The persistence of calcium release under conditions where the membrane was permeable to both anions and cations makes it unlikely that this phenomenon is due to a changing transmembrane potential.     

Hypothalamic sarcoidosis and hypopituitarism

4 patients with presumed pituitary hypothalamic sarcoidosis are described. 3 had histological diagnoses compatible with sarcoidosis and in the other this diagnosis was strongly suspected from chest X-rays. 2 patients presented with diabetes insipidus. ACTH reserve was diminished in 3 out of 4 and growth hormone reserve was diminished in the 3 who were tested. All 4 patients developed secondary amenorrhea. 3 patients had hypothalamic hypothyroidism. Prolactin dynamics were intact. Tomograms of the sella turcica in all 4 and computerized tomography of the hypothalamic area in 2 patients failed to reveal any abnormality.     

Regulation of IgE antibody production by serum molecules. IV. Complete Freund's adjuvant induces both enhancing and suppressive activities detectable in the serum of low and high responder mice.

Two biologically active serum molecules manifesting precisely opposite biologic effects, both of which are selective for IgE antibody synthesis, can be detected in the serum and ascites fluids of CFA-immune mice. One activity, described previously, is suppressive and hence termed suppressive factor of allergy (SFA); the other, reported for the first time herein, is enhancing and has been termed enhancing factor of allergy (EFA). The ability to detect one vs the other activity requires certain special manipulations such as different doses of low dose x-irradiation. Conclusive evidence for the existence of two distinct factors mediating these two opposing biologic effects was obtained in studies demonstrating that affinity chromatography on concanavalin A-Sepharose segregated the two molecular entities. Thus, SFA binds poorly or not at all to Con A-Sepharose, whereas EFA binds to Con A and can be recovered in the eluate eluted with the competitive sugar alpha-methyl-D-glucopyranoside.     

Adaptive differentiation of murine lymphocytes. III. T and B lymphocytes display reciprocal preference for one another to develop optimal interacting partner cell sets.

Responses to the synthetic terpolymer L-glutanmic acid, L-lysine, L-phenylalanine (GLphi) and hapten derivatives thereof are controlled by two complementing H-2 linked Ir genes in the mouse. F1 hybrids derived from two different nonresponder strains (one of which possesses the alpha and the other beta Ir-GLphi gene) are phenotypic responders to GLphi and 2,4-dinitrophenyl (DNP)-GLphi. Moreover, spleen cells from DNP-GLphi-primed F1 mice can adoptively transfer secondary anti-DNP antibody responses to irradiate been challenged with DNP-GLphi. When, however, GLphi-primed F1 helper T cells are transfered together with the DNP-specific F1 B cells that had been primed in separate mice altogether by DNP coupled to an unrelated protein carrier, such mixtures failed to develop adequate adoptive secondary anti-DNP responses to DNP-GLphi. This contrasted with the ability of the same GLphi-primed F1 T cells to provide helper activity for DNP-primed B cells from responder recombinant B10.A (5R) mice. More important, the apparent defect of GLphi-primed F1 T cells in providing help for DNP-primed F1 B cells (primed to a DNP-protein conjugate) could be readily overcome by using DNP-primed B cells from donor F1 mice primed with DNP-GLphi. As discussed herein, these results suggest that interacting T and B lymphocytes pair off into partner cell sets, any pair of which interact optimally when a "best fit" reciprocal self-recognition occurs between them.     

The effect of calmodulin on the phosphoprotein intermediate of Mg2+-dependent Ca2+-stimulated adenosine triphosphatase in human erythrocyte membranes.

The effect of calmodulin on the formation and decomposition of the Ca2+-dependent phosphoprotein intermediate of the (Mg2+ + Ca2+)-dependent ATPase in erythrocyte membranes was investigated. In the presence of 60 microM-Ca2+ and 25 microM-MgCl2, calmodulin (0.5-1.5 microgram) did not alter the steady-state concentration of the phosphoprotein, but increased its rate of decomposition. Higher calmodulin concentrations significantly decreased the steady-state concentration of phosphoprotein. Calmodulin (0.5-1.7 microgram) increased Ca2+-transport ATPase activity by increasing the turnover rate of its phosphoprotein intermediate. Increasing the MgCl2 concentration from 25 microM to 250 microM increased the (Mg2+ + Ca2+)-dependent ATPase activity, but decreased the concentration of the phosphoprotein intermediate. Similarly to calmodulin, MgCl2 increased the turnover rate of the Ca2+-transport ATPase complex (about 3-fold). At the higher MgCl2 concentration calmodulin did not further affect the decomposition of the phosphoprotein intermediate. It was concluded that both calmodulin and MgCl2 increase the turnover of the Ca2+-pump by enhancing the decomposition of the Ca2+-dependent phosphoprotein intermediate.     

Circadian rhythms in juvenile american shad, Alosa sapidissima

Swimming activity (in cm s⁻¹) of a school (55 individuals) of young-of-the-year ( total length=110 mm) American shad, Alosa sapidissima , was determined under a variety of photoperiod conditions. These included a normal (ambient), a shifted, and constant-light day. Swimming activity was measured over 4-day periods. During normal days swimming speeds followed periods of about 24 h, with fast speeds (up to 45 cm s⁻¹) and schooling occurring during the photoperiod. Under dark conditions speeds were slower (8 cm s⁻¹) with most fish swimming as individuals. During a shifted day swimming speeds and schooling corresponded to the imposed day. Under constant light (equivalent to bright moonlight) no schooling was evident, and a constant, but slow, swimming speed was observed in each 24-h period. These shad demonstrated an exogenous rhythm with respect to the imposed day length. It is hypothesized that an endogenous circadian rhythm would only be of use to a fish required to hunt or chase its prey. Shad, being plankton feeders, do not chase prey and therefore can exhibit an exogenous circadian rhythm with no detrimental feeding results.