Survival of plant mitochondria in vitro. Form and function after 4 days at 25 degrees C

The energy-dependent maintenance of morphological and functional integrity by avocado mitochondria during incubation for 4 days at 25 °C is confirmed by (1) sustained levels of oxidation, phosphorylation, and respiratory control; (2) membrane intactness as evidenced by three diagnostic enzymes: succinate:cytochrome c, NADH:cytochrome c, and α-ketoglutarate:K₃Fe(CN)₆ oxidoreductase; and (3) the retention of physical properties as shown by rate-zonal centrifugation and electron microscopy. Some changes do occur in the mitochondrial population during the 4 days. These include an increase in density and the conversion of some organelles to dumbbell shapes. Bacterial growth, though difficult to control, does not appear to be directly responsible for the eventual loss of energy-linked functions.     

Senescence of Pear Fruit Cells Cultured in a Continuously Renewed, Auxin-deprived Medium

Auxins and cytokinins support cell division in tissue and cell cultures. In cytokinin-independent pear (Pyrus communis) cells, omission of 2,4-dichlorophenoxyacetic acid (2,4-D) from the medium for two successive transfers leads to rapid cell lysis, unless the osmolarity is raised to 0.4 molar with mannitol. Use of this system (nutrients plus mannitol minus 2,4-D) for the study of cell senescence was explored both in batch culture and in a system designed to permit medium renewal without withdrawal of live cells.     

Serological analysis of species specificity in the high mobility group chromosomal proteins.

The non-histone chromosomal protein of the high mobility group (HMG-1) present in mouse liver was purified to homogeneity. Antibodies against this protein as well as pure HMG-1 derived from calf thymus and HMG-E purified from duck erythrocytes were elicited in rabbits. The interaction between the antibodies and the immunogens was measured by passive hemoagglutination and by quantitative microcomplement fixation. Quantitative microcomplement fixation assays revealed that the immunological distance between HMG-1 from calf thymus and HMG-1 from mouse liver and duck erythrocytes was 15. This corresponds to 3% sequence differences. It was estimated that amino acid substitution occurred at about seven positions in the polypeptide chain. Thus, HMG-1 proteins display remarkable evolutionary conservation in their primary sequence, similar to that displayed by histones H4 and H3, suggesting that their biological function is dependent on stringent structural requirements. HMG-E protein is significantly different from both HMG-1 and HMG-2 derived from calf thymus. As such, it is a protein unique to avian erythrocytes.     

Life history of mouse sperm protein. Intratesticular stages

A basic protein fraction, migrating as a single band in acetic acid-urea gel, distinct from histones, was isolated from mouse sperm collected from vasa deferentia and caudae epididymides and was used to immunize female rabbits. The presence of antibodies to the mouse sperm protein (MSP) in the rabbit antisera was demonstrated by a cytoimmunofluorescence procedure using the cells of origin of the antigenic protein, the mature mouse sperm. The specificity of the antisera was verified by fluid and gel precipitation tests and by crossed immunoelectrophoresis. The latter procedure demonstrated the presence of two antigen-antibody systems, consonant with earlier reports that the basic chromosomal protein of mouse sperm is heterogeneous. MSP antigen in situ was recognized by the specific antibodies of the rabbit antisera only after the smear of mature sperm was treated with either of two reducing agents: 2-mercaptoethanol or dithiothreitol. However, when the immunofluorescence procedure was applied to untreated smears of mouse testicular cells, spermatids of all stages from 1 to 14-15 were positive, while spermatocytes, stage 16 spermatids and spermatozoa were negative. After treatment of testes smears with reducing agent, only spermatocytes remained negative. Those observations indicate the following: (a) MSP is immunogenic in a heterologous species; (b) its antigenic sites are detectable in spermatozoa and spermatids of all stages, but not in primary spermatocytes; (c) those antigenic sites become masked at about stage 15 of spermiogenesis and may be unmasked by treatment with a reducing agent. The interpretation is made, therefore, that one or more components of MSP are assembled at the beginning of spermiogenesis and undergo an alteration in the final intratesticular stage of spermatid maturation. That alteration may be presumed to be the formation of disulfide linkages between the cysteine residues.     

Immunogenic changes of murine lymphoma cells following in vitro treatment with aryl-triazene derivatives

Summary A series of dimethyl aryl-triazene derivatives and related monomethyl compounds were studied for their efficacy in mediating a strong increase in immunogenicity (i.e., chemical xenogenization, CX) of murine leukemic cells following in vitro treatment. It was found that all compounds under investigation were able to induce CX. The dimethyl derivatives were able to induce CX only after metabolic activation, whereas related monomethyl compounds were active per se.The antigenicity acquired by triazene-treated leukemic cells was very marked; intact hosts histocompatible with the parental line were able to reject up to 10⁷ cells. Antigenic tumor cells retained their immunogenic properties even after a large number of transplant generations in the absence of the drug. This means that marked immunogenicity of triazene-treated cells is a stable and heritable characteristic.     

Cell-mediated immunity to chemically xenogenized tumors. II. Evidence for accessory function and self-antigen presentation by a highly immunogenic tumor variant

To determine whether antigen-presenting ability might be involved in the superior immunogenicity of chemically xenogenized tumors over that of parental cells, we tested a murine lymphoma line xenogenized by a triazene derivative for expression of Ia antigens, ability to present soluble antigen in vitro, and production of factor(s) active in a mouse thymocyte assay. Results showed that Ia antigens, absent on nonimmunogenic parental L5178Y cells, were expressed on a xenogenized, highly immunogenic tumor variant (clone D), as detected by immunofluorescence. While the ability of parental cells to stimulate lymphocyte proliferation in vitro was lost on removal of Ia+ cells from the responder population, considerable augmentation of reactivity was observed upon depletion of Ia+ cells from the population of splenocytes responding to the xenogenized cells. Under these conditions, stimulation was blocked by anti-Ia antibodies, or an anti-L3T4 reagent or antibodies to the novel antigenic determinants induced by xenogenization. In addition, no stimulating activity was observed following exposure of clone D cells to glutaraldehyde or lysosomotropic agents such as chloroquine and ammonia. When the ability of clone D cells to present ovalbumin in vitro was assayed, it was found that the xenogenized cells could present the soluble antigen to specifically primed lymphocytes. Moreover, clone D cells could substitute for splenic adherent cells in the proliferative reaction of splenocytes to concanavalin A. Finally, when the supernate from clone D-cell culture pulsed with phorbol myristic acetate was tested in a mouse thymocyte assay, considerable IL-1-like activity was disclosed.     

Fine Structure of Antennal Sensilla of Paysandisia archon and Electrophysiological Responses to Volatile Compounds Associated with Host Palms

Paysandisia archon (Lepidoptera: Castniidae) is a serious pest of palm trees. A comprehensive knowledge of the insect olfactory system is essential for the development of efficient semiochemical-based control methods. The olfactory sensilla are located particularly on the antennae, and these can detect plant volatiles that provide important cues for the insects in the search for their host plants. To date, the fine structure of P. archon antennal sensilla studies and their role in host-plant perception have not been investigated in great detail. Using light microscopy and scanning and transmission electron microscopy, the antennae of both sexes of P. archon are described here in detail, according to the different types, quantities and distributions of the sensilla. Six types of sensilla were identified. The most widespread are sensilla trichoidea, sensilla basiconica and sensilla auricilica, which are associated with olfactory function. These have cuticular shafts characterised by numerous pores, and they are innervated by two or three sensory neurons. Sensilla coeloconica, sensilla chaetica and sensilla ampullacea are associated with olfactory or olfactory-thermoreception, mechano-gustatory, and thermo-hygroreception functions, respectively. Moreover, the role of P. archon antennae in locating of the host palms was evaluated using electroantennograms, to monitor responses to ester and terpene compounds previously identified as volatiles of damaged/fermenting palm tissues. P. archon showed responses to all of the synthetic chemicals tested, with greater responses in the females, providing a significant sex*dose effect. Among the compounds tested, ethyl isobutyrate elicited the strongest antenna responses. The fine structure of the cuticular and cellular components of the P. archon antenna sensory equipment is described for the first time. The results of this study form an important starting point and complement physiological and behavioural studies, to provide valuable information of practical importance for the development of efficient semiochemical-based control methods.