Characterization of the calcium sensitivity of differentiation in SCC-13 human squamous carcinoma cells

Summary The sensitivity to calcium of the human squamous carcinoma cell line, SCC-13, was demonstrated and characterized. Cultures grown to confluence in the presence of 0.2 to 2 mM calcium had approximately 10-fold higher levels of particulate transglutaminase activity and envelope competence than those grown in low calcium (0.025 to 0.05 mM) medium. Raising the calcium from 0.025 to 1.8 mM induced expression of this enzyme and of competence over the course of a week. Conversely, for cultures grown to confluence in 1.8 mM calcium, subsequent reduction of calcium to 0.025 mM resulted in a substantial decline in transglutaminase over a similar time period. Immunoprecipitable transglutaminase was clearly identifiable in cultures grown in 1.8 mM calcium-containing medium but not in those grown in low calcium medium or in the presence of retinoic acid, suggestive of regulation at the level of mRNA accumulation or translation rather than posttranslational modification. This research was supported by Public Health Service grant AR 27130 from the National Institute of Arthritis, Musculoskeletal and Skin Diseases, Bethesda, MD, and National Research Service postdoctoral fellowship ES 05336 from the National Institute of Environmental Health Sciences, Research Triangle Park, NC.     

The preparation in vitro of chrysanthemum for transplantation to soil

Plantlets of Dendranthema grandiflora Pennine Reel were grown from nodal sections on Sorbarods saturated with liquid medium containing 0–3 mg 1^–1 of various growth retardants. After 4 weeks they were transferred to compost and maintained at a relative humidity of 42% at 27.5°C. Wilting was assessed over a period of 3 h. Plantlets treated with paclobutrazol, flurprimidol, triapenthenol, chlorphonium chloride, uniconazol and ancymidol showed dose-related reductions in wilting up to a concentration of 3 mg 1^–1. Responses to tetcyclacis and mepiquat chloride were weaker, and no responses to chlormequat chloride, BTS 44584 or diaminozide could be detected. These observations are compatible with an hypothesis that resistance to wilting derives from inhibited synthesis of gibberellins.     

Dark matter in the solar system: Hydrogen cyanide polymers

In the presence of a base such as ammonia liquid HCN (bp 25 °C) polymerizes readily to a black solid from which a yellow-brown powder can be extracted by water and further hydrolyzed to yield-amino acids. These macromolecules could be major components of the dark matter observed on many bodies in the outer solar system. The non-volatile black crust of comet Halley, for example, may consist largely of such polymers, since the original presence on cometary nuclei of frozen volatiles such as methane, ammonia, and water makes them possible sites for the formation and condensed-phase polymerization of hydrogen cyanide. It seems likely, too, that HCN polymers are among the dark —CN bearing solids identified spectroscopically by Cruikshanket al. in the dust of some other comets, on the surfaces of several asteroids of spectral class D, within the rings of Uranus, and covering the dark hemisphere of Saturn's satellite Iapetus. HCN polymerization could account also for the yellow-orange-brown coloration of Jupiter and Saturn, as well as for the orange haze high in Titan's atmosphere. Implications for prebiotic chemistry are profound. Primitive Earth may have been covered by HCN polymers through cometary bombardment or terrestrial synthesis, producing a proteinaceous matrix that promoted the molecular interactions leading to the emergence of life.     

Elemental and isotopic analyses of mammalian fauna from Southern Africa and their implications for paleodietary research

Elemental analyses of mammalian bone (e.g., strontium-calcium ratios, or Sr/Ca) distinguish between herbivores and carnivores; however, the relationships among herbivores are unclear. To study this question, a modern faunal sample from the Nagupande Tsetse Control Area (Zambezi drainage, Northwestern Zimbabwe) was used. This collection has the advantage of well-established geographical controls in addition to a varied fauna, which includes both bovids and suids. The grazing/browsing dietary status of each species was ascertained by means of isotopic analysis of carbon. Clear differences were seen in the δ¹³C of grazing and browsing animals; a specialized grazer was found to have significantly lower Sr/Ca than less specialized grazers and browsers. In this study it was also possible to examine differences in Sr/Ca by sex; female warthogs were found to have significantly lower Sr/Ca than males. The variation in certain animal groups was found to be abnormal. Implications for reconstruction of prehistoric human diets using trace-element techniques are discussed.     

The structure of the basement membrane of human lymph node high endothelial venules: An ultrastructural, histochemical and immunocytochemical study

Summary The structure of the basement membrane of the high endothelium of reactive human lymph nodes was investigated by techniques selective for carbohydrates (periodic acid-Schiff; critical electrolyte concentration staining with Alcian Blue; lectin histochemistry), specific proteins (immunohistochemistry for laminin and fibronectin) and by conventional techniques of light and transmission electron microscopy. Adjacent small lymphocytes were assigned to B and T cell subsets by use of monoclonal antibodies and they were analysed for non-specific esterase,-glucuronidase,-N-acetylglucaminidase and proteolytic activities. The basement membranes were shown to be distinctive and to contain three layers, of differing laminin, glycosaminoglycan and glycoprotein oligosaccharide content. Certain lymphocytes (probably T) contained enzymes potentially able to degrade some components of these basement membranes.     

Thermodynamic analysis of the lactose repressor-operator DNA interaction

Kinetic and equilibrium constants for lactose repressor-operator DNA interaction have been examined as a function of salt concentration, size and sequence context of the operator DNA, and temperature. Significant salt effects were observed on kinetic and equilibrium parameters for pLA 322-8, an operator-containing derivative of pBR 322, and pIQ, an operator and pseudooperator-containing derivative of pBR 322. The association rate constant and equilibrium constant for the 40 base pair operator fragment were also salt dependent. Data for all the DNAs were consistent with a sliding mechanism for repressor-operator association/dissociation [Berg, O. G., & Blomberg, C. (1978) Biophys. Chem. 8, 271-280]. Calculation of the number of ionic interactions based on salt dependence yielded a value of approximately 8 for repressor binding to pIQ and pLA 322-8 vs. approximately 6 for the repressor-40 base pair fragment. These data and the differences in binding parameters for the plasmids vs. the 40 base pair operator are consistent with the formation of an intramolecular ternary complex in the plasmid DNAs. Unusual biphasic temperature dependence was observed in the equilibrium and dissociation rate constants for pLA 322-8, pIQ, and the 40 base pair fragment. These observations coupled with a discontinuity found in the inducer association rate constant as a function of temperature suggest a structural change in the protein. The large positive entropy contributions associated with repressor binding to all the DNAs examined provide the significant driving force for the reaction and are consistent with involvement of ionic and apolar interactions in complex formation.     

Sex ratio and intrasexual kin competition in mammals

Summary Asymmetries in both intrasexual competition and generation overlap occur in Antechinus (Dasyuridae; Marsupialia). We show that the range of interpopulation variation in the sex ratio of pouch young spans and exceeds the range of sex ratios at birth hitherto recorded from eutherians (Clutton-Brock and Albon 1983). Although postweaning dispersal and male mortality are similar among all Antechinus populations, interpopulation variance in female longevity leads to variable duration of mother/daughter interaction. As this duration increases, parental investment is increasingly biased toward males, supporting the view that local competition among female kin for resources may influence mammalian sex ratios.     

Computer-Assisted Image Analysis of Plant Growth, Thigmomorphogenesis, and Gravitropism

A nonintrusive auxonometric system, based on the DARWIN image processor (Telewski et al. 1983 Plant Physiol 72: 177-181), is described and demonstrated in the analysis of gravitropism and thigmomorphogenesis in corn seedlings (Zea mays). Using this system, growth and bending of regularly shaped plants or organs can be quickly and accurately measured without, in any way, interfering with the plant. Furthermore, the growth and bending curves are automatically plotted. Thigmomorphogenesis in the aerial part of corn seedlings involves growth promotion at a low force load and growth retardation at higher force loads. The time courses of the two kinds of response are somewhat different, with retardation occurring immeditely after mechanical perturbation and growth promotion taking somewhat longer to begin. Gravitropic experiments show that when dark-grown corn seedlings are placed on their side in the light, the resulting curvature is due to two consecutive morphological mechanisms. In the first instance, lasting for about 15 minutes, the elongation of the bottom edge of the plant accelerates, while the elongation of the top edge remains constant. After that, for the next 1.75 hours, the elongation of the top edge decelerates and stops while that of the bottom edge remains constant at the increased rate for most of the period. The measurements taken from both experiments at relatively high resolution (0.08-0.1 millimeter) show that the growth curves are not smooth but show many small irregularities which may or may not involve micronutations.