Class II MHC molecules and the HIV gp 120 envelope protein interact with functionally distinct regions of the CD4 molecule.

A murine T cell hybridoma with a receptor specific for the class I molecule H-2 Dd was transfected with an expressible cDNA for human CD4. Expression of the human class II MHC molecule HLA-DP on Dd-positive murine fibroblasts resulted in a greatly enhanced response of the CD4-positive T cell hybridoma, measured either by lymphokine production or by rosette formation. Inhibition of these functional assays with anti-CD4 monoclonal antibodies implicated the two amino-terminal domains of CD4 in an interaction with the HLA-DP molecule. This interaction was blocked by incubation with recombinant gp120 envelope protein of HIV. In contrast, recombinant soluble CD4 did not inhibit and was able to prevent the inhibition by gp120. Anti-CD4 antibody blocking experiments clearly indicated that distinct regions of CD4 interact respectively with gp120 and with class II MHC molecules.     

Stable-light producingEscherichia coli

Summary Stable light production inEscherichia coli is achieved by cloning the genes encoding bacterial luciferase fromVibrio harveyi. To gain advantage of sensitive detection of light we transferred the genes under the control of a regulatable promoter system and searched for growth and buffer conditions where bacteria emitted stable light. Based on our findings an automated biosensor system can be developed to monitor the effects of biologically active compounds against stable-light producing bacteria.     

Plant regeneration and somaclonal variation from cultured immature embryos of sister lines of rye and triticale differing in their content of heterochromatin

Summary Plants were regenerated from cultured immature embryos of two pairs of sister lines of triticale (X Triticosecale) cvs Rosner and Drira and five sister lines of rye (Secale cereale). The triticale lines differ in heterochromatic content of a particular rye chromosome (6R or 7R), while the rye lines differ in only one heterochromatic band. Variation in morphogenetic response was present between the triticale cultivars and between the rye lines. One of the rye lines (7RL+ +) showed a distinctive superior response in terms of somatic embryogenesis. These findings are discussed in relation to factors affecting morphogenetic response and genetic stability in culture.     

Production of somatic hybrids by electrofusion in Solanum

Summary Conditions are described for large scale electrofusion of mesophyll protoplasts of dihaploid S. tuberosum with those of diploid S. brevidens. Overall fusion frequencies of 20%–30% were achieved, and following fusion, large numbers of protoplast-derived calli were obtained. Putative somatic hybrid plants were selected from the regenerated shoots by examining their morphological characteristics. Twenty-one somatic hybrids were confirmed by isoenzyme analysis and six somatic hybrids were further confirmed by Southern hybridization. Tetraploid hybrids were obtained, but cytogenetic studies indicated that more of the regenerated hybrids were hexaploid than had previously been found following chemical fusion of the same partners. Some advantages of electrofusion over chemical fusion are discussed.     

Platelet peripheral benzodiazepine receptors in repeated stress.

[3H]PK 11195 binding to platelet membranes and plasma stress hormones were studied in soldiers at the beginning of a parachute training course, following 6 days of preparatory exercises, and after the fourth actual parachute jump. A slight reduction (15%; NS) in the number of peripheral benzodiazepine receptors (PBR) was detected at the end of the exercise period, prior to the first jump. Reduced (26%; P less than 0.05) density of PBR was observed immediately after the repeated actual jumps. Equilibrium dissociation constants were not affected by the stressful situation. Plasma cortisol and prolactin levels remained unaltered during the entire study period.     

Biochemical characterization of a spearmint mutant that resembles peppermint in monoterpene content

A radiation-induced mutant of Scotch spearmint (Mentha × gracilis) was shown to produce an essential oil containing principally C3-oxygenated p-menthane monoterpenes that are typical of peppermint, instead of the C6-oxygenated monoterpene family characteristic of spearmint. In vitro measurement of all of the enzymes responsible for the production of both the C3-oxygenated and C6-oxygenated families of monoterpenes from the common precursor (−)-limonene indicated that a virtually identical complement of enzymes was present in wild type and mutant, with the exception of the microsomal, cytochrome P-450-dependent (−)-limonene hydroxylase; the C6-hydroxylase producing (−)-trans-carveol in the wild type had been replaced by a C3-hydroxylase producing (−)-trans-isopiperitenol in the mutant. Additionally, the mutant, but not the wild type, could carry out the cytochrome P-450-dependent epoxidation of the α,β-unsaturated bond of the ketones formed via C3-hydroxylation. Although present in the wild type, the enzymes of the C3-pathway that convert trans-isopiperitenol to menthol isomers are synthetically inactive because of the absence of the key C3-oxygenated intermediate generated by hydroxylation of limonene. These results, which clarify the origins of the C3- and C6-oxygenation patterns, also allow correction of a number of earlier biogenetic proposals for the formation of monoterpenes in Mentha.     

The molecular analyses of an antimorphic mutation of Drosophila melanogaster, Scutoid

A dominant mutation of Drosophila melanogaster, Scutoid (Sco), acts as an antimorphic allele of the no-ocelli (noc) gene. In Sco the noc region has been transposed from 35B to 35D on chromosome arm 2L and the noc gene is now adjacent to snail (sna). Induced revertants of Sco are frequently mutant for sna or are aberrations broken very close to sna. A molecular analysis of the Sco chromosome has confirmed that noc is transposed and fused to the sna region. However, only part of the noc region is included within the transposition. The breakpoints of 19 chromosomally aberrant Sco revertants have been mapped at the molecular level. Fourteen of these breakpoints map to the noc region, spread over about 80 kb of DNA. The breakpoints of the remaining five are not within the DNA of the noc region and appear to map within sequences from the sna region. This has been shown directly for three of these, those associated with T(2;3)ScoR+13, In(2L)ScoR+24 and In(2L)ScoR+26. Thus mutation of either noc or sna, genes which are apparently unrelated in their wild-type functions, can revert the antimorphic phenotype of Sco.     

Isolation of secretory cells from plant glandular trichomes and their use in biosynthetic studies of monoterpenes and other gland products.

The natural products that accumulate in or exude from plant glandular trichomes are biosynthesized by secretory cells located at the apex of the trichome. To investigate the formation of glandular trichome constituents in several species of mints (Lamiaceae), a new procedure was developed for isolating large numbers of highly purified secretory cells. In this method, the leaf surface is gently abraded with glass beads in a way that fragments the glandular trichomes and yields clusters of intact secretory cells. The isolated, intact secretory cells and cell-free preparations derived from them are very active in monoterpene biosynthesis and provide useful starting materials for the purification of several key enzymes of monoterpene metabolism. The procedure described is adaptable to a broad range of plant species and should find wide application in the preparation of whole cell and cell-free systems for biosynthetic studies of plant natural products found in glandular trichomes.     

Mutations within the uncE gene affecting assembly of the F1F0-ATPase of Escherichia coli.

Activation of protein kinase C (PKC) in human T lymphocytes is an immediate consequence of mitogenic signalling via the antigen-receptor complex and CD2 antigen. In order to investigate further the signal-transduction pathways which result in PKC activation, we have established a novel PKC assay system using streptolysin-O-permeabilized T cells. Known peptide substrates of PKC were introduced into permeabilized cells in the presence of [gamma-32P]ATP, 3 mM-Mg2+ and 150 nM free Ca2+. The peptide found to have the lowest background phosphorylation had the sequence Pro-Leu-Ser-Arg-Thr-Leu-Ser-Val-Ala-Ala-Lys-Lys (peptide GS), and the phosphorylation of the peptide was increased up to 6-fold by direct activation of PKC with phorbol 12,13-dibutyrate. Induction of PKC activation with the UCHT1 antibody against the CD3 antigen, or with phytohaemagglutinin (PHA) or guanosine 5'-[gamma-thio]triphosphate (GTP[S]), increased peptide-GS phosphorylation by 2-3 fold. The specificity of PKC action on peptide GS was demonstrated by blocking increases in phosphorylation with a pseudosubstrate peptide PKC inhibitor. PKC activation by this technique could be detected within 1 min of adding external ligand. Dose-response curves revealed that PHA-induced production of inositol phosphates correlated closely with PKC activities, whereas only a partial correlation between these parameters was observed with GTP[S]. Our data are consistent with the presence of more than one G-protein-mediated pathway of PKC regulation in T cells. The quantitative PKC assay system described is both simple and reproducible, and its potential application to a wide range of cell types should prove useful in further investigations of PKC activation mechanisms.