In vitro regeneration of apomictic bluestem grasses

Explants from immature inflorescences of four genotypes of Old World bluestem grasses, (Bothriochloa spp.), produced callus tissue on Linsmaier and Skoog (RM) and 1/2 Murashige and Skoog (1/2 MS) media containing high levels of growth regulators. Callus masses were composed of two distinct tissue types, one a compact, white, embryogenic portion (E calli), the other soft, translucent, gelatinous and nonembryogenic (NE calli). When transferred to medium with a reduced level of 2,4-D, and/or supplemented with zeatin, E callus underwent further organization culminating in shoot production. Light and scanning electron microscopy confirmed the embryogenic pathway of differentiation. Genotype significantly affected callus induction frequency and the number of plants regenerated. The RM medium induced more explants to initiate callus compared to the 1/2 MS medium. Age of the inflorescence explant, as indicated by size, was critical for callus induction. Inflorescences with racemes 8 mm in length were superior to older ones. Five-hundred-twenty-two plantlets were regenerated and grown to maturity.     

Triphenylethylene antiestrogen binding sites (TABS) specificity

The relative binding affinities (RBA) of various compounds for the triphenylethylene antiestrogen binding sites (TABS) were examined. The ability of tamoxifen to inhibit the binding of [3H]tamoxifen to salt extracted (0.4 M KCl) TABS from rat liver nuclei was used as a standard by which other compounds were compared (tamoxifen RBA, 100; Kd approximately 1 nM). Nafoxidine was the most effective triphenylethylene compound used (RBA 333; Kd approximately 0.3 nM) whereas the RBA of zuclomiphene and enclomiphene was not different from tamoxifen. MER-29 was the weakest inhibitor of the triphenylethylene derivatives (RBA 10; Kd approximately 10 nM). Trifluoperazine, chlorpromazine and the anti-calmodulin drugs W-13 and W-12 had RBA's of 25, 1, 1 and 0.1 respectively. The binding affinities of cholesterol and 7-ketocholesterol were significant (Kd approximately 22 nM) while the steroid hormones, estradiol, testosterone, progesterone and corticosterone displayed not observable affinity. Various compounds obtained from Merrill Dow Pharmaceuticals and the Eli Lilly Company which contained alklaminoethoxy side chains linked to aromatic ring structures had RBA's ranging from 1-0.3. We conclude, as other investigators have also concluded, that the similar binding affinities of various triphenylethylene antiestrogens for TABS and their divergent activities as antiestrogens makes it unlikely that TABS are directly involved in estrogen antagonism. The moderate but significant affinity of TABS for trifluoperazine and other drugs thought to be involved in calmodulin regulation indicates that TABS may be a linked in some way to calmodulin function. The binding of cholesterol and 7-ketocholesterol is also significant and may indicate that TABS are involved in cholesterol metabolism.     

Replication of cauliflower mosaic virus DNA in leaves and suspension culture protoplasts of cotton

Cauliflower mosaic virus (CaMV) replicated in protoplasts and in inoculated leaves of the non-host, cotton (Gossypium hirsutum, L.). Protoplasts prepared from suspension-cultured cotton cells were infected by incubation with liposome-encapsulated CaMV virions. During a 1-week culture period the amount of CaMV nucleic acid as detected by nucleic acid hybridization in the protoplasts increased significantly regardless of whether or not the protoplasts contained vacuoles. In leaves inoculated with CaMV virions or CaMV DNA, viral DNA sequences were found by leaf skeleton hybridization to be located in small circular areas. DNA extracted from ultracentrifugal pellets of homogenates of inoculated leaves contained circular, gapped CaMV DNA only when inocula contained CaMV virions, CaMV DNA, or partial nested dimer CaMV plasmid DNA. When plants had been heavily watered, the CaMV DNA recovered contained degraded CaMV DNA. The results suggest that the host range limitation for CaMV is not due to an inability to replicate or spread locally in inoculated leaves.     

Sugar transport by the bacterial phosphotransferase system. Reconstitution of inducer exclusion in Salmonella typhimurium membrane vesicles

The accompanying articles (Saffen, D.W., Presper, K.A., Doering, T.L., and Roseman, S. (1987) J. Biol. Chem. 262, 16241-16253; Mitchell, W.J., Saffen, D. W., and Roseman, S. (1987) J. Biol. Chem. 262, 16254-16260) show that "inducer exclusion" in intact cells of Escherichia coli is regulated by IIIGlc, a protein encoded by the crr gene of the phosphoenolpyruvate:glycose phosphotransferase system (PTS). The present studies attempt to show a direct effect of IIIGlc on non-PTS transport systems. Inner membrane vesicles prepared from a wild type strain of Salmonella typhimurium (pts+), carrying the E. coli lactose operon on an episome, showed respiration-dependent accumulation of methyl-beta-D-thiogalactopyranoside (TMG) via the lactose permease. In the presence of methyl-alpha-D-glucopyranoside or other PTS sugars, TMG uptake was reduced by an amount which was dependent on the relative concentrations of IIIGlc and lactose permease in the vesicles. The endogenous IIIGlc concentration in these vesicles was in the range 5-10 microM, similar to that found in whole cells. Methyl-alpha-glucoside had no effect on lactose permease activity in vesicles prepared from a deletion mutant strain lacking the soluble PTS proteins Enzyme I, HPr, and IIIGlc. One or more of the pure proteins could be inserted into the mutant vesicles; when one of the two electrophoretically distinguishable forms of the phosphocarrier protein, IIIGlc Slow, was inserted, both the initial rate and steady state level of TMG accumulation were reduced by up to 40%. The second electrophoretic form, IIIGlc Fast, had much less effect. A direct relationship was observed between the intravesicular concentration of IIIGlc Slow and the extent of inhibition of the lactose permease. No inhibition was observed when IIIGlc Slow was added to the outside of the vesicles, indicating that the site of interaction with the lactose permease is accessible only from the inner face of the membrane. In addition to the lactose permease, IIIGlc Slow was found to inhibit both the galactose and the melibiose permeases. Uptake of proline, on the other hand, was unaffected. The results are therefore consistent with an hypothesis that dephosphorylated IIIGlc Slow is an inhibitor of certain non-PTS permeases.     

Importance of immunoglobulin isotype in therapy of experimental autoimmune encephalomyelitis with monoclonal anti-CD4 antibody

Experimental allergic encephalomyelitis (EAE) is an autoimmune disease mediated by CD4+ T cells. Prior studies have established that monoclonal anti-CD4 antibodies can reverse EAE. To determine whether immunoglobulin isotype plays a role in the therapy of EAE with anti-CD4 antibody, an isotype switch variant family of the mouse IgG1 anti-rat CD4 antibody W3/25 was isolated with the fluorescence-activated cell sorter. The IgG1, IgG2b, and IgG2a W3/25 isotype variants all had identical binding capacities for rat CD4+ T cells. Although all three W3/25 isotypes showed some beneficial effects in the amelioration of EAE, the IgG1 and IgG2a W3/25 antibodies were superior to the IgG2b W3/25 in the treatment of EAE. Multiparameter fluorescence-activated cell sorter analysis of T cell subpopulations from treated rats showed that none of the antibodies of the W3/25 isotype switch variant family substantially depleted CD4+ target cells in vivo. These experiments demonstrate that immunoglobulin isotype is important in the monoclonal antibody therapy of autoimmune disease. They indicate that therapy of EAE may be successful without a major depletion of CD4+ lymphocytes. Immunotherapy may be optimized by selecting an appropriate isotype of a monoclonal antibody.     

Genetic analysis of murine strains C57BL/6J and C3H/HeJ to confirm the map position ofAth-1, a gene determining atherosclerosis susceptibility

Previous results suggested that strains C57BL/6J and C3H/HeJ differed in a single gene for atherosclerosis susceptibility, calledAth-1. Based on data from recombinant inbred strainsAth-1 was tentatively assigned to chromosome 1 linked toAlp-2. In this report, a cross between C57BL/6 and C3H/HeJ was carried out in order to test whether the tentative map position was correct. Parental strains and F₁ and F₂ progeny were examined. Susceptible alleles ofAth-1, found in C57BL/6, are associated with relatively low levels of high-density lipoprotein (HDL)-cholesterol in animals fed an atherogenic diet; resistant alleles ofAth-1 are associated with relatively high levels of HDL-cholesterol. F₁ progeny have HDL levels that are intermediate between these of the two parental strains. Among the F₂ progeny,Alp-2 andAth-1 cosegregated, providing confirmatory evidence thatAth-1 is linked toAlp-2 on chromosome 1. Three mice recombinant forAlp-2 andAth-1 were found among the 60 chromosomes tested, giving an estimated map distance between these two genes of 5.0±2.8 (SE) cM. The phenotypic characteristics ofAth-1 resemble a genetic trait in humans, hyperalphalipoproteinemia, which is characterized by elevated levels of HDL-cholesterol, reduced risk of heart disease, and increased longevity.This work was supported by Grant HL-32087 from the Heart, Lung, and Blood Institute, National Institutes of Health, Grant 1858 from the Council for Tobacco Research, Grant 86-1387 from the American Heart Association with funds contributed in part by the Alameda, Orange, and Santa Barbara County Chapters, and Grants 85-N132A and 85-N136A from the California Affiliate of the American Heart Association.     

p82H identifies sequences at every human centromere

Summary A cloned alphoid sequence, p82H, hybridizes in situ to the centromere of every human chromosome. After washing under stringent conditions, no more than 8% of the grains are located on any specific chromosome. p82H thus differs from other centromeric sequences which are reported to be chromosome specific, because it detects sequences that are conserved among the chromosomes. Two experimental approaches show that the p82H sequences are closely associated with the centromere. First, p82H remains with the relocated centromeres in an inv(19) and an inv(6) chromosome. Second, p82H hybridizes at the centromere but not to the centromeric heterochromatin of chromosomes 1, 9 and 16 that have elongated 1qh, 9qh and 16qh regions produced by short growth in 5-azacytidine. The only noncentromeric site of hybridization is at the distal end of the 9qh region.     

Antigen recognition in autoimmune encephalomyelitis and the potential for peptide-mediated immunotherapy

Peptide binding and lymph node T cell activation studies have been used to characterize T cell recognition of an encephalitogenic T cell autoantigen from myelin basic protein in (PL/J x SJL)F1 mice. Amino acids that determine interactions with either the restriction element of the major histocompatibility complex (MHC) or the encephalitogenic T cell receptor are defined. This information enables the design of peptides that bind MHC yet do not cross-react with the autoantigen. A peptide analog of the encephalitogenic epitope is shown to be "heteroclitic" for MHC binding and activation of encephalitogenic T cells in vitro. This analog is not immunogenic for encephalitogenic T cells in vivo and is shown to inhibit disease that is induced by the autoantigen itself.